Hot Water Recirculating Loop
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- Опубликовано: 26 сен 2019
- How to cut the wait for hot water in bathrooms that are a long way from the water heater. I added a return line from two locations, through a check valve, into the bottom of the heater, setting up a circulation of hot water that does not require a pump.
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Thanks! So I watched this video a few months ago. I was replacing old rusty galvanized pipes in my ranch style home with pex, and I decided to make a hot water loop to supply all my fixtures and then return to water heater drain as you explained. I missed the part about the check valve somehow. My water was actually fairly warm all the time but never hot. You could actually take a shower and not turn on the cold water and it was Ok, just OK. On my own, I decided I needed a check valve on the return line and installed it yesterday. This morning, my water in the master bath was cold for the first time in a couple of months. I tracked down your video and rewatched it, and saw the part about the check valve modification, so I'll be drilling the hole in the flapper today. Hopefully, that will fix the problem. Thanks again!! Also, one other modification I'm making is adding a shut-off valve in the return line that can be timer and wifi controlled. That way I can disable the recirculation at night, and when we're away from the house for extended periods, and save a little gas.
I'm getting ready to replace CPVC with Pex and wanted to add recirculating line without a pump. Back in the 70's I built a ranch house and a plumber friend did this for me on that house and it worked great. Thanks for posting this.
I installed a system like this, using a pump, and it works great. Very cool seeing the gravity design working. I used a spring-loaded check valve and didn't do the hole (if you can even do that on the design of flow check I used) but I've heard multiple reasons for the hole in the check valve, such as preventing valve chatter on pumped systems (for the hydronic heating loop in my house, there are check valves that were previously installed for whatever reason, and you hear a metallic clanging sound while the heat is running, which may be from these check valves, although I'm not sure), or for preventing an air lock in the system, which could be a concern in your system, since the gravity circulation would probably stop if you had an air lock in the recirculating line. With the hole, you're probably pulling a small amount of hot water the opposite direction while using any hot water at the tap, from the bottom of the WH, to the open fixture, which would ensure any air lock is bled out. The downside of reverse flow for your design is pretty low, since the water is warm anyway because you tee-d into the drain port, so you don't have the risk of cold water bleeding over into the hot line when there's a large enough pressure drop in the hot line. Your design also eliminates the power and design complexity needed for a pump, and keeps the water constantly circulating, which will increase the amount of hot water you have available, as well as prevent the risk of pipes freezing in winter, since the water at the very bottom of the tank will now be warmer than it was before. Cool to see you did it all in copper; I was lazy and used pex on mine 😅
this works great, I've had that system for over twenty yrs on my oil fired hot water tank... yrs ago I wanted to buy a circulating pump and an old plumber explained this to me. nothing to wear out or break down.
Interesting. An old time plumber told me about such a system about 30 years ago, but according to his explanation, it only works if the end points are higher elevation than the water heater such as water heater in the basement or crawl space and return lines are eitler level or sloped downward. Based on the theory of heat rises. Very interesting if you can get this to work with water heater on same floor as end points.
I’ve got to install this! One tied in on my Dad’s side sink in the master, the laundry room, and one for the kitchen sink would do it.
AMAZING! I was looking for the concept and I found your video. Thank you!
This is brilliant thank you. I was considering installing a recirculating pump, but I definitely will be doing this instead.
So did it work out. Or do I just need to buy the pump instead. Thanks
Best description I could have hoped for. Thank you!
Looks like you’ve got a lot of time & $ invested into your home - looks fantastic!
Thank you!
Excellent video!
If your water is from a well with a pump, this will save on energy to run the pump and wear and tear on the pump.
Note: if you have a tankless water heater, gravity recirculation might not be enough to turn on the heater.
This seems like a perfect thing to use with the Uponor logic system I've been researching.
since I don't have access to any lines, no basement of attic, I think I will add a 2.5 gallon Water heater fed from the hot water supply line at the 70 foot away bathroom... Installed in the kids bedroom closet which backs up to the bathroom.
But I really love your detailed explanation and I will be doing what you detailed for our master, just 20 feet. Electric isn't a concern since I have solar.
Coldwater pipes are insulated to keep them from dripping condensate.
Your statement is true, however generally there shouldn't be a high enough dew point in your home to form condensation on your cold water pipes. If that is happening you need a dehumidifier. You should be able to just enslate the hot water pipes to retain the heat
Right anwser
Very well explained.
Did this to our house when we remodelled...works great. WH is in the crawl space, upstairs' showers get hot water in 5 seconds or less. Used 3/4" pex on the main loop, 1/2" pex on branch lines and insulated it all well. I always thought the water recirculated due to the temperature differential versus gravity...but I might be wrong. Either way, it works. Nice to not have a pump that can go out.
Heat rises. Cold sinks. Unrelated to gravity.
@@D_Syno Gravity is the source of "up" and "down," "rise" and "sink." Without gravity, heat doesn't rise and cold won't sink. Therefore, the system described is a gravity system.
Great explanation. I'm planning on installing a tankless Navien water heater that has an internal recirculation or external recirculation. I'm planning on doing the external.
Have you installed your navien tankless system yet?
Ey buddy I got a question, did you put a pump for this sistem or just the tank doing by itself?
Good video! That's another project for the list!
Also all that extra waste water could eventually cause a septic system to collapse! Just happened to my neighbor.
Insulating the cold is a de facto requirement, especially with a finished ceiling. If they didn't insulate the cold, there will be a trail of water under every cold water run from water in the air condensing on the cold water pipe, no different than water condensing in an air conditioning system and running out of the drain hose. The hot is normally only insulated if you recirculate.
Using gravity like gravity hot water heat works, but I'm not totally convinced as there are other reasons for that pipe being hot. However, I did find at askthebuilder that they outlined exactly what you did, and I do thank you for your thoughts and the effort you put into making this video.
I notice in the comments that people are trying to come up with a cost basis as to this not costing more or the cost minimized. They need to get over it. You are trading energy money for convenience. To say you are money by saving water is laughable. Unless your house runs on bottled water, that's spending a dollar to save a hundredth of a penny. The only variable is how to get acceptable performance for the least energy investment.
If your water is from a well with a pump, this will save on energy to run the pump and wear and tear on the pump.
I thought the return was mixed in with the cold water inlet. It looks like you supplied it where you empty out the hot water heater
In my system, I installed the ball valve above the check valve so when need service the check valve, I won't need to turn off the main valve.
Will this approach work for a 2-story house? I wonder there’s enough “gravity” to use this approach. Is insulting the hot side the trick to make this approach working? Or, do you insulate both hot and the return?
Here’s quick estimation:
0.5” pipe, 8 ft up for hot (80 deg C, very hot) and 8 ft down for cold (40 deg C, like hot summer day). The water weight difference of water in the cold and hot is about 6 grams or 0.0132 lbs. the pressure from this delta on 0.5” check valve is about 0.07 psi, which is never strong enough to open a check valve with 1.5 psi opening threshold. So, you have to have a small hole in the flipper of the valve. Does this make sense?
Thanks.
Math is on point! I particularly appreciate the mix of Imperial and metric units. The small 'leak' drilled in the check valve allows a small constant flow (which might be temporarily reversed when the hot tap is opened.) The check valve still stops most of the cold-side flow from reversing.
Hi Owen thanks for the video and nice work. I was wondering I’ve seen some hot return lines tee back into the cold inlet line feeding into the tank, off course with check valves installed on both lines. Have you witness this before and know if there is any hassles with it?
This is my setup and I'm wondering if it's causing my water heater to run more often. With the recirc pump on the cold inlet actually becomes warm, despite a check valve in place to prevent backflow. I guess they're mixing together like pouring hot and cold water into a cup.
@@joshwaloveslotr Its no problem at all to tee into the the top of the water heater cold inlet...it all goes str8 to the bottom of the heater via the dip tube inside. It's fine to tee into the drain outlet as well but the system in this video doesn't have a die-electric union installed....he just used a brass nipple....which is NOT a substitute. Circulating systems, for reasons unknown, cause pin-holes in copper piping, so not having a die-electric union only increases the chances of pin-hole repairs.
Me? I just ran a dedicated 1/2" hot water line to my furthest fixture (Kitchen sink) so it takes about 20 secs for piping hot water to arrive. I insulated it too so that it stays hot for about 30 mins of non use.....best thing I ever did.
I ran a 1/4" inch line from my heater to my one of my master sinks for that early morning hot water demand for washing face, brushing teeth etc. Takes 5 secs for that water to arrive.
Can I use 1/2” PEX for the return line. I realize it’s really 3/8” copper equivalent. I have a 30’ return distance from farthest fixture and only one leg.
I'm planning to install this system in my rancher with the water heater in the 5' crawl space. It would be a single looped system. I have purchased two backflow preventers, one of them would be mounted vertically and with the spring removed making it position in a normally open flow and only close on a backflow condition. One valve is a all brass construction and the other is a brass body with a polyethylene tappet inside. What are your thoughts on witch one to use?
Can u do this at every far from water heater fixture & manifold them into the drain of water heater?....or is it just for 1 far fixture?....
So I was dead set on installing a recirculating hot water loop using the expensive $550 On demand TACO Genie pump and $100 motion sensors 4 of them. Now this new gravity recirculating systems has me on a mind roller coaster. I see this is better since there are no future pump maintenance cost. I wonder what are the cons? I was thinking to do one big loop ( about 75-90 feet of running PEX A pipe (UPONOR PEX)) since all plumbing is exposed. Any thoughts?
Yes, should work fine. The return line can be small such as 1/2 inch because you are expecting low volume. A 'con' is that you are keeping the hot lines hot/warm all of the time, which takes energy. My new 2005 home has a recirculation set up during construction, with pump and thermostat to control the pump. I decided to stop using the pump and because of the "heat rise" physics mentioned here, it still circulated. Bonus - no electricity required. The home furnaces (3), h/w heaters (2 in series) and stove run on propane. When I turned the recirculation valve off, I found that my propane usage year-to-year was cut in half! I specified that all pipes - hot, cold, recirculate - would be insulated. Owen mentioned this trade-off in his discussion - just didn't quantify it.
Without a timer this loop is constant so water heater (mine is electric) would run longer. Are there valves with timers? So the loop basically expands the size of the water heater by the volume of water in the lines. Therefore you'd want those lines insulated REAL WELL, but would insulating the rtn lines retard the gravity force?
Realistically, you want all lines well insulated. All of mine are, and I still get "gravity" circulation with water heater in 2nd story attic and demand on 1st story at the opposite end of the house. I have a pump but don't have it turned on - water flows right through because it has no internal valving such as a spring-loaded check valve. If you still want to use a pump, there are many options. Solar systems have a created a market for 12V pumps (which can be driven by a wall-wart transformer), and temperature sensor based relays. If you prefer, you can use a wall-outlet-based timer to plug the wall-wart into, which then powers the pump. Some of those timers have an internal clock that keeps on ticking if you loose power so you don't have to reset its clock when power resumes. You could even combine these two controls (time and temp) to activate a pump if you want that type of sophistication.
So if I'm understanding this correctly, this is more efficient because the water that is returned to the bottom of the heater is still fairly warm so it requires less energy to heat it up to the desired temperature compared to cold water?
This set-up is more to save water, at the cost of a small amount of water heating fuel. Instead of dumping the (cooled) contents of the hot-water supply line, this loop circulates the hot water continually so it doesn't go cold from sitting in the pipe. If the pipes are insulated, the water shouldn't cool too much, but a small loss is unavoidable.
Re: *Gravity* Hot Water Recirculating
Will this work if the hot water lines are ran under the crawlspace? Withe the water heater located above?
I'm wondering, do you suppose the water heater is still coming on more often, now that you've insulated the pipes?
A year later & I'm wondering the same. My copper pipes are non insulated, keeping the heat in those would have to see the hws on-times increasing.
If you had a pump then you could have it set to come on at peak times only (when you expect someone may need hot water). I suppose you could install an electric valve e to do the same job on your gravity system.
Nice job. I have the same problem
Good video and demonstration.. wondering if the trade off of gas vs water is worth it? Probably is. I'm a plumber myself, just looking up different opinions and ideas on the topic
I am a plumber also, Saint Louis area. I’m doing a little pro bono job for a friend and I really hate putting in something that I know it was going to wear out and potentially cause issues so I’m trying to figure out the best way to keep everything simple. Keeping it simple would be putting in a 1/16th hp pump for a total of a 90 foot loop with a couple of swing checks, insulating the lines very well, leaving the pump run 24 hours a day. I feel like there has to be a better way. The best line out the last 10 linear feet or so of the return line going to the base of the water heater needs to be on insulated. I guess I’m trying to ask you what you decided to do or what some of your research might have uncovered. I’m a big commercial industrial guy And I love figuring this kind of stuff out!
🤙
@@562handsomemike well since I’ve been working for a new company and we use navien tankless water heaters. And you can set the recirc in half hour increments and set it day by day. We usually set the recirc to set 7 days a week to run about 530-6am to 930-10pm. You can change each day individually if you’d even want to incase someone is not home for days at a time.. seems to be most efficient rather than some pumps not running off a timer and just temperature. The navien tankless also has an option to learn your schedule and will then the recirc will only run at typical times you use it.
@@562handsomemike Gravity loop with a check valve is going to wear out?
I own a ranch that needs this badly. I noticed in your video your return was swichted to 1/2". Was that on purpose? I was going to run my return in 3/4". I didn't notice was your feed line 1/2" or 3/4"?
Return is low demand / low volume. All you want is a path for the water to return. The larger the lines are, the more heat will be lost - it's a physics / geometry issue because all hot/warm lines will have heat loss.
@@bobblack3870 1/2” copper or 1/2” PEX? Either work based on your comment I would think then? If all it needs is a return path?
@@bobs4718 Sure, 1/2" will work fine but is overkill for homes. For many homes, this is likely to be standard for the final end-point usage, especially items like showers. Sinks may even be using 3/8". If you have it or want to go smaller, 3/8 or even 1/4 will work, because the return circulation like does not need high volume.
@@bobblack3870 thanks, are there any issues with slight elevation variations in the return line? I will need to dip about 10” and back up 10” for 12’ half way back to my HWH.
@@bobs4718 No issues.
I think a recirculation pump, that's on a timer or a push button start, or a IR sensor start, that only comes on when needed, may use less gas. If it's only recirculating the cold/hot water, 5 - 10 minutes before you need the hot water You will save more Natural Gas. Those small recirculation pumps only use a few dollars of power per year, if used only on demand. Could you compare your hot water gas bill, before and after your return line, to see the average cost difference.
In my country, hot water cylinders are never installed further than 6 meters from point of use to minimise the "dead leg".
Also, the fewer fittings on your water supply lines, the better, your pressure and flow are reduced with every bend and tee you use. (Average pressure in our homes is 400-600kpa). 🍻🇿🇦👍
This system wouldn’t work with an instantaneous hot water heater (with no stored hot water) would it? What are the alternatives?
The problem is the tankless water heaters need minimum 2.5 psi water pressure to turn on. That's the issue I'm trying to solve now so I can install a tankless to supply a Dickinson Radex forced air hot water heater in an rv. Trying to find a 12v CONTINUOUS hot water pump that can handle pumping hot water and not over heat and shut down...
Genius! I must do this! My wife complains and wastes mass water at the kitchen to get hot water.
Thanks a lot.
Its no problem at all to tee into the the top of the water heater cold inlet...it all goes str8 to the bottom of the heater via the dip tube inside. It's fine to tee into the drain outlet as well but the system in this video doesn't have a die-electric union installed....he just used a brass nipple....which is NOT a substitute. Circulating systems, for reasons unknown, cause pin-holes in copper piping, so not having a die-electric union only increases the chances of pin-hole repairs.
Me? I just ran a dedicated 1/2" hot water line to my furthest fixture (Kitchen sink) so it takes about 20 secs for piping hot water to arrive. I insulated it too so that it stays hot for about 30 mins of non use.....best thing I ever did.
I ran a 1/4" inch line from my heater to one of my master sinks for that early morning hot water demand for washing face, brushing teeth etc. Takes 5 secs for that water to arrive.
Does this only work if the plumbing is above the water heater to use gravity? How about a house where all of the plumbing is run under the house in a crawl space while the WH is on grade with the living area?
I am in that same situation and would love to hear someone's experience with this. OC Run, did you ever get a response to this?
@@wimchalmet No I didn't get any response. If you find it out would you mind posting it here?
@@ocrun6765 My house, built in 1940, is plumbed like this. A brass nipple piped into the water heater drain just like this video showed. The house is pier-and-beam and plumbing runs under the house through the crawl space as well as to 2nd story bathroom where shower gives hot water in about 2-3 seconds. Have always loved it. Been here 20 years.
@@jeffbonner2765 thanks for your response.
Hi Owen-thanks for this video! I just had my plumber install a new water heater and a recirculating pump. It was taking 5 minutes to get hot water to my shower in the MB. Problem is that now I have the opposite problem. Hot (scalding) water first then cold. Once cold it stays cold and can't adjust to warm water. I've turned down the water heater..which now only gives cold water to the shower. Sinks seem to distribute hot/cold ok...but shower not good! Any suggestions? My plumbers are stumped and have said they've never seen this happen so they don't know how to fix it. Meanwhile, I've spent $700 on the pump. I love my plumbers and they've tried hard to make it right..they are stumped! Thanks for any help!
After reading, my question is if a check valve was installed. In addition, be sure to have a cutoff valve so you can disable recirculation entirely. Then my next question is to determine if the plumber ended up connecting somewhere between hot/recirculate and cold lines somewhere in the house. My new home plumber did. He marked nothing and at one point I asked him what was what and he said "I'm not sure." Because I have white CPVC everywhere, before insulation was installed in my new house, I took 3 cans of spray paint (blue, red, pink) and squirted spots on the lines at various points as I tried to trace what was what during construction. I got confused so I quit. Now after the house is built and the plumber gone, I have done more review of his work because of freezing issues and found more incompetence in design. To diagnose your situation, cutoff the recirculation line and confirm that the shower works. Then cutoff the hot water line at the water tank - you should not be able to draw any water from any hot faucet or any shower. If I recirculate to get the loop hot, I can flush the master toilet and it will be filled with hot water!
This works very well, but it’s actually not a gravity system, it’s a thermal loop system.
Hot water from the tank has a path all the way to the faucet/shower and back to the bottom (cold part) of the tank. Provided this loop is uninterrupted AND the hot water tank is heating the water, you will get a constant cycle of water.
If the water is not heated, the cycle will stop - because it’s not a gravity system, it’s a thermal loop system.
IIRC, such a system will not work if there is a jog in the hot water plumbing whereby the pipe 90’s down and then back up again, as this causes a thermal block.
A gate-valve is nice to have, as it allows you to reduce the flow of the hot water in this loop to just enough to provide wait-times that you are happy with, thereby saving energy.
There is no limit (that I am aware of) for how far the fixture can be, but the farther it is, the more heat-loss and therefore energy usage.
Well depends how you look at it. Cold water is more dense, therefore heavier than hot water. Without a gravitational force this loop would not work.
@@JEZPP I stand corrected, you are right, it is the more dense and therefore heavier cold water that falls to the bottom of the system that propels the thermal loop. Without gravity, this colder/heavier water would not fall to the bottom.
Thank you for the correction!
@@user-qn6yt3zx3w yes, I've always been somewhat amazed how it seems that gravity has a roll in almost every part of physics, biology, chemistry, etc... without gravity many thing would not be possible.
Is it going to work if you have 3 loops? I have ranch house and I need to do 3 instead of 1 long one ?
Like three separate branches to bathrooms? Should be fine. Mine has two branches and they tee together about 10 feet upstream of the check valve. Both zones stay nice and hot.
But, why would the water move without a circulation pump? It's pressurized evenly throughout.
The cooler water in the return pipe near the heater moves slowly downward due to the temperature difference, pulling hot water from the heater outlet around the loop and through the check valve. Pumped return lines are common too, but I was impressed that this concept works as well as it does. Thanks for watching!
So the water just moves on it's own????
this setup may increase pipe heat loss. the hot water pipes should be insulated when a recirculating loop is used.
Pipes are now insulated (except the last 8 feet or so at the water heater) - no pump in this setup, which I'm pleased about. Gravity powered!
@@owenperkins Please, explain. How to use this system without recirculating pump ? You mean, it is enough to have some slopes for this? But what about the head which should be created by pump for delivering water from heater to
Sink ?
@@turquthuseynov9323 Maybe I can help. I have a recirculation line in my 2 story house. Water heaters are in a 2nd story attic. Master shower/bath is 1st floor on the opposite end of the house and it still works, even though I have a pump on the recirculation return line and the pump is turned off. Apparently the temp difference between the hot water heater's inlet @ bottom and it's outlet @ top is enough to cause circulation. Heat rises, cold water (cooling off in the lines) sinks.
Wow thats a cool brass p trap in the background. With a copper vent. Looks pricey.
I'm no expert but seems to me this would work best if your heater was at the lowest point of the loop. You need the heat source low to make the water flow up otherwise the hot water may get trapped at the highest part of the loop and not flow back down.
That is as worthy thought. However I have a recirculation line in my 2 story house. Water heaters are in a 2nd story attic. Master shower/bath is 1st floor on the opposite end of the house and it still works. Apparently the temp difference between the hot water heater inlet @ bottom and it's outlet @ top is enough to cause circulation.
yes I would agree it is s must that DHWH is at the low point, which means rancher style with crawl spaces won't work if the DHWH is on the same floor, damn, haha.
That's alot of extra work to install
One can install a pump at the hot water heater side then you gonna have plenty of water all the time.
the convection style of water recirculation doesn't work real well for all situations. for a single level house, the action of water heating isn't enough to push it all the way back. just install a pump
Insulate the pipe. Don't insulate the last portion to the heater. Will work perfect in 1 story house. Don't trap hot lines. No issues
Finally! I think I've found the reason why the previous homeowner installed an additional 1/2" line to the bottom of the water heater! Except ours has a ball valve and not a check valve, which would make sense why we get cold water out of the farthest faucet when another faucet is drawing hot water, like a shower.
Yup, just add a check valve in line with the recirc return loop right before it tees back into the bottom of the WH and you should be good. If your system is gravity and doesn't have a pump, you'll want to use the same style of valve that Owen used in the video which doesn't have a spring and doesn't require any force to open the check valve. If you don't want to solder/sweat copper, you can use a Shark Bite fitting, but I think Shark Bite only makes a spring loaded check valve which may not work for a gravity/non pumped system unfortunately. You can also try mostly closing the ball valve, which will limit the amount of water that's able to flow in reverse through the recirculating loop, and will make the water at the further fixture somewhat warmer without modifying the current system.
@@MittyNuke1 yeah, I tried the shark bite check valve. Even though it's only about a 2 psi check, it will not let the water gravity circulate. I took it out and put a straight-through union in place until I can find the correct one.
So why didn’t you use a recirc pump?
Many water heaters these days have thermal traps in them, and recirc pumps don't work from what I've read. This system works great if you have the ability to add the extra piping. Adding pex is cheap, quick, and easy.
It will work fine without the check valve.
I thought the old bar room looked better...
They maybe wanted to warm up the space with hot water pipes
the return pipe should be on grade(with fall) with the high point at the fixture end
😔
My water heater is right off the kitchen, I do think gas is more efficient with producing heat than electric 🤔
At current utility rates you are absolutely right. If your house is laid out so the kitchen and bathroom(s) are close to the water heater, you may not have a problem with hot water taking a long time to reach the fixtures, and you wouldn't need this setup. Thanks for watching! :)
Owen Perkins I’ve actually had an experience with no electricity for 9 days due to an ice storm in Kentucky. The house got down to 40 degrees. Thankfully we had a gas water heater and we had hot water. So every time I look at homes, a gas water heater is a must have. Because it sucks to not have it when you need it the most 😂
@@nathanielaranda8407 9 days?? Wow...hopefully that was a once in a lifetime occurrence. Otherwise an automatic standby generator would be on my short list of home improvements.
Owen Perkins it was back in January of 2009. Our local Walmart and Lowe’s had power, so we would just shop around to get warm. It was hilarious, they were like can I help you find anything. We said no were just trying to get warm 😂
In a video for people interested in saving time, how about creating your drawings and script ahead of time.
Water is cheaper than gas so I guess I'll stick to wasting more water.
A lot of water is more expensive than a little bit of gas.
@@mr2981 not if your gas is running constantly.
All depends on your location, in mine, we'd rather waste gas; it's cheaper than water.
And in my case if you have well water. That's "free" water so I can't justify pumping cold water back into the bottom portion of my electric water heater. "Free" water versus more use of electricity. Correct me please.
Think of it this way. It's much cheaper to keep a hot water loop warm than reheating a bunch of water. All the water you let run down the drain while you're waiting for warm water is also replaced at the water heater with cold water. So not only are you wasting water that's already been heated but got cold, your water heater needs to reheat that amount of water again plus the hot you actually use. It waste twice the energy and water.
Don’t use a check on gravity recirc.