PC Q&A: Expansion Tanks for Tankless Water Heaters
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- Опубликовано: 22 ноя 2022
- Welcome to a brand new segment on this channel, which I like to call "PlumbingsCool Q&A"! And it's exactly what it sound like!
It's my hope I can build a quick and (relatively) simple video format to help answer or elaborate upon, the many questions I have the privilege of receive from viewers around the world.
My goal is for this format to less formal and simpler than my usual videos and shorts (don't worry; those aren't going anywhere!). Think of it as your very own Plumbing & Mechanical classroom!
So let's see how this little experiment goes! In any event, please do reach out to me in the comments section to let me know your own thoughts on "PCQ&A" (good or bad!)...or perhaps you have your own question or curiosity. Well, ask away, then, and I'll do my best to address it.
We'll kick off this first Q&A segment with a question from viewer, Fri Sung, who wants to know whether expansion tanks can (or should) be installed onto tankless water heaters as well as traditional tank heaters installed with check valves. For more context, please feel free to have a quick view of my Short on thermal expansion, which you can find right here:
• Stop Thermal Expansion...
MYTHBUSTER WATER HEATER VIDEO:
Also - as promised in the video - here's a You'tube link to a Myth Busters segment, that demonstrates the dire repercussions of excessive pressure buildup in a traditional water heater. I strongly encourage you to take four minutes and watch it; I promise that you'll never look at your water heater the same way again! 😁
• MythBusters - Explodin...
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#Watts #Thermal Expansion #WaterHeater
Thank you, your explanation was very clear.
Thank you! Your kind of encouraging feedback is what it's all about! 🙏
Thanks. Very clear explanation of why.
Pleasure!
Very well presented. This was clear and easy to follow. You sir, are a born instructor! Thank you.
Thank you so much for your encouraging words! 🙏
Just wanted to say thanks after watching couple of your other vids, copper flaring and swaging. Very helpful!
Thanks so very much! 🙏 I'm delighted you found them useful. Stay tuned, as there's much more to come!
Totally makes sense--Thank you for the video
Thank YOU!
Great explanation. Very very helpful diagrams.
Thanks for the inspiring words! 🙏 Delighted that you found it useful!
Thank you, informative, information I needed.
Thanks so much for your positive feedback! 🙏 Above all, I'm grateful to know that it helped you!
Thank you for this video. A plumber just suggested that I get an expansion tank installed just this morning!
Awesome! I hope it resolves your issue.
Great video. I thought you had missed one thing. There are check valves withing the tankless water heater that I would have thought meant you have to put the expansion tank on the hot water side. However, looking at your diagram the thermal expansion that does occur with the recirculating loop is still relieved by the expansion tank on the cold water side. Thanks for the video.
Thanks for your feedback and insight!
Thanks so much for explaining this!! My townhouse has an expansion tank with my Rinnani on demand water heater so I wonder why they built it this way! I’m at 7200’ elavation
7200 feet elevation!...WOW! 😲
Still, your elevation shouldn't be a coarse for your requiring an expansion tank. My guess is that somewhere along your cold water inlet (before your Rinnai) is a check valve...or perhaps even a backflow preventer? (which essentially both do the same thing: prevent water from flowing in reverse direction.). If that's the case, then the expansion tank would prevent any buildup in static pressure (although you shouldn't be getting much thermal expansion since the water is heated only as required).
very good video, does the expansion tank have to be on the warm side of the tank? Would the cold like be fine aswell as previously with expanding back out to the utilities?
Thank you! 🙏. You can absolutely put it on the cold side AS LONG AS it's downstream (after) any check valves which may exist on the cold side, so that there is nothing obstructing the expanding water and the tank.
Here's a Short which I hope may help elaborate what I'm trying to express:
ruclips.net/user/shortspGCPExUvxLs?si=0TxPsOf_SpvBjrQV
Does the expansion tank need to be installed on the cold side before the water heater or on the hot side after the water heater? Thanks! Awesome videos! Merry Christmas! 🎄🎁
Technically, where the expansion tank gets installed doesn't really matter because the pressure will equalize evenly throughout (provided there's no other check valve in between). However, if I were splitting hairs, I'd rather put it on the cold side because (at least in my mind) I'm willing to bet that the constant exposure to hotter water may shorten the lifespan of the internal bladder, compared to only cold water. But that's just my opinion; these tanks are approved for both cold and hot water applications (such as with hydronic in-floor heating).
Hope this helps. Thanks for the inspiring words! 🙏 Merry Christmas to you too! All the best! 🥂
@@PlumbingsCool Awesome! Thank you for the swift response! MERRY CHRISTMAS!🎄🎉
Thanks
Great video! I have a tankless system with an expansion tank thats bladder has failed ( small black particles coming out from the tubs hot water faucet while filling the tub). Can I just have the expansion tank removed or should I have a new one put in to replace it? Thanks so much!
Glad the video helped! With respect to your current situation, it would be tricky to assess without becoming familiarized with your entire system. If you are confident that you bladder tank has indeed failed, I'd begin by remedying the obvious - which is to replace the bladder tank. I'd be weary about outright eliminating it, because I'm presuming it was initially installed for a reason.Most importantly, if you have any sort of device installed upstream (before) the water distribution system which prevents your water from expanding (such as a check valve, backflow preventer, or pressure reducing valve), then you should most definitely have the bladder tank replaced and not outright eliminated. On the other hand, if your bladder tank HAS indeed failed, then you've been operating without one for quite some time already, and you've noticed no other symptoms with your system (other than the black specks), then uninstalling it outright might be a possibility.
You don't necessarily need to do any major modifications to your plumbing to test out whether or not you require an expansion tank, because the tank connects via a screwed connection (likely a 3/4" male thread). You can simply isolate and drain-down your system, unscrew the bladder tank, and plug up the connection with a threaded BRASS (NOT steel!) plug. This way, you can always remove the plug and replace it with a new bladder tank.
But at the end of the day, I'd simply replace the bladder tank with a new one if you can't accurately assess whether or not you require one, as they're relatively inexpensive and simple to replace.
Hope this helps!
great video. would love for you explain reverse plumbing or first in last out in a cascading tankless hot water setting. lets say you install 3 units in a row, does the master unit always fire first or does reverse plumbing prevent this and units will alternate? or is it all software? thanks for your insight.
Thanks very much! 🙏 To your question, by cascading, I presume you're referring to setting up the water heaters in parallel (as opposed to series, which would cause them all to fire, but the first one will endure the by far the brunt of the work - I'm not sure why anyone would want to connect in series).
Presuming that all three are connected in true parallel (all connecting piping being of equal lengths, distances, and fittings), then they should fire equally and at the same time. I'm honestly not sure of there's a way to have them fire independently or in alteration as you suggest, although I can imagine that it could be done with some sort of timed solenoid valve configuration, which could allow the cold water feed to be redirected in turn.
Thank you nonethess for your interesting question!
@@PlumbingsCool yes with on demand water heaters like rinnai in many instances especially commercial you would hang more than one I. A row. They are supposed to turn on based on demand so they all may not fire at once.
A little off topic but how do you feel about on location instant hot water heater's such as under the kitchen sink. Any suggestions or maybe a video?
Good video by the way.👍🍻
Hey, thanks for the feedback! 🙏
With respect to your on-demand water heater question: Are you referring to the Insinkerator Instant Hot units that dispense near-boiling water on demand through a separate little faucet, for teas, soups, etc...or the little electric tanks which serve as the primary hot water for the main kitchen faucet?
@@PlumbingsCool The separate faucet units.
Any opinions on the Insinkerator? The reviews are all over the place.
Having both owned them and installed them across several decades, I certainly do have some opinions on Insinkerator's Instant Hot units.
As much as I like Instant Hot dispensers, they are somewhat of a luxury product, and thus they charge you quite the premium, considering what little they provide you and their questionable lifespan.
The biggest problem with them is that they WILL fail after a few years...and I recall Insinkerator even stating so in their manuals many years back.
Two issues may occur:
1. The tank element will burn out (and is irreparable, unlike traditional larger electric water heaters). It's nothing more than a tank with an 120V electric embedded in low-density Styrofoam).
2. The tank will leak.
The leaking issues have gotten better over the years, as they at least make them out of stainless steel, last I checked (they were once made out of copper, and then someone got the bright idea to start making them out of plastic, which was a complete disaster: You could outright taste the plastic leeching into the water, and the tanks would split after a short while.
If/when the tank does fail, you could by the tank only, but the cost will still set you back about $400..
If you're ok with the upfront and potential eventual expenses, then go for it. They're an awesome convenience when everything goes well...only be aware of their potential for failure (I think they provide a measly one year warranty).
Also, if your unit comes with their filter, you may want to consider replacing the filter system with an aftermarket filtration system or outright bypass it altogether: There's nothing wrong with their filters, but their replacement filters are atrociously expensive, given that it's nothing more than a simple carbon filter.
Hope this helps!
@@PlumbingsCool Thank you! I've installed a couple of these types of heaters, different brands, but having never owned one, wasn't aware of the issues they have.
Considering the cost, seems like they should be made better. Maybe I'll hold off for a while to see if improvements are made. Thanks again. 👍🍻
thx for the explanation.
why the small instant hot water heaters for kitchen require an Open Vent faucet? (what exactly is an open vent faucet?) And is it ok to install a bladder and use a regular faucet?
It's interesting...I've never seen them referred to as "open vent faucets", but I'm pretty sure I know what you mean:
The instant water heaters you're referring to are likely those point-of-use models that get installed right underneath the kitchen sink, and are useful for when small volumes of REALLY hot water are required (up to 210F), such as for making tea or Cup-a-Soup. They're often made by Inskerator.
If you're referring to those, they often come with their own special faucet that allows water to escape through the faucet itself to relieve pressure in the inevitable event of thermal expansion. I've had those Instant Hot systems myself for several years, and I remember being puzzled the first time I witnessed my faucet sputtering water!...until I figured out what was going on (I don't think the manuals warn you about that!).
In any event, I can't verify whether an expansion tank will work in this this case, because there's a possibility that those Instant Hots have check valves built into them (which would negate any upstream protection). But I can't be sure without further investigation or calling the company.
It's probably still your best best to use one of the legacy faucets that are designed for the system, which will remove the need for additional protection via an expansion tank.
And yes, I'm aware that those Insinkerator faucets are a pretty penny...especially when you start getting into the non-chrome finishes! 🤯
Hope this helpsl
@@PlumbingsCool I appreciate your input.
Are check valves usually visible? Also, I was gonna install the NPE-240A2 with a recirculation pump built in and a sensor valve installed under my sink. Do you think I need an expansion tank with this set up?
It's difficult for me to assess your situation. Traditional check valves are usually noticeable by following the water lines and looking for them that way. Some recirculation pumps have built-in check valves which may be hidden in the pump's outlet. Your best bet is probably to check your unit's and equipment's owner's manual, to get a clearer idea of the requirements. The bottom line is that if the heating water is getting trapped in any way (there is no avenue for expansion), then you will need an expansion tank to accommodate the expansion. Some signs might be intermittently-leaking temperature & pressure relief valves, as I demonstrated in this Short:
ruclips.net/video/pGCPExUvxLs/видео.htmlsi=vLhq8Wx_vt0PVUfn
Hope this helps!
@@PlumbingsCool thanks for getting back with me!
Thank you so much for sharing your video, my house is a 10 years old, we just changed to the Timeless one months ago, we don't know why after the Timeless cause a house that has a water hammer, we don't have a disconnect issue before。 second floor Cosmo issue, every time after you wash your hand Wendy turn off the water you heard about the noise， we tried to drain the water from the pipe, Osterville Ethan, the first five minutes the noise is gone then come back again， the dishwash no problem but the laundry wash is really noisy， Wonder heater we do have a extension tank。 but we don't have it on the hot water line。 is the Tankless do we need to install the Extension tank on the hot water line?or water hammer rest?
Do you have any idea better?
Hi there. It's difficult to diagnose your problem without additional details, but one thing that does stand out for me is that you mention water hammer when operating the clothes washer. It should NOT be associated with the fact that you have a tankless heater instead of a traditional water tank.
Water hammer usually the result of your water pressure being too high: When the high flow of water is stopped suddenly, then that energy from the flowing water transfers to the pipes (which creates the "Bang!") Although an expansion tank would help with water hammer, you usually install dedicated "water hammer arrestors" onto the hot and cold water lines serving the fixtures that are causing water hammer, which usually consist of fast-closing valves - among the most notorious being washing machines and single-lever shower/bathtub valves.
If your water pressure is too high (over 80 PSI), then the best solution is to reduce the pressure by installing a pressure-reducing valve (PRV). To learn more about a simple to measure your water pressure and installing a PRV, you can check out my video here:
ruclips.net/video/_dBLKHrOE98/видео.html
Hope this helps!
@@PlumbingsCool
Thank you for your reply.
We have hot and cold water hammer assester on the washing machine as well as one for the dish washer
We have lower the main pressure to 40-45 psi and even installed a thermal expansion tank on the cold domestic side and still hammer
We used to have a Navien combi tankless and a electric water tank
The chasis cracked and we replaced it with a Rinnia combi with out a storage tank.
Do we need to install a storage tank?
Hmmm...not too sure. I noticed that you mentioned both an "expansion" tank, as well as a "storage" tank, which are two different things.
I'll never be able to provide you with a definitive answer without a closer inspection of your system, but if you did actually mean "storage" tank, I'm not sure why you'd need one as it would eliminate the entire point of having an "on-demand" water heating system. The combi unit should have been sized large enough to handle your total hot water requirement without having to pre-heat and store water.
Hello, I somewhat understand. I'm looking to install a tankless water heater for my home. It's a navienA2 series (with a recric in it) no dedicated recirculating line (going to install a bypass under sink). No check valve on line. Only for domestic water. Do I need an expansion tank for the water heater? (Sorry for all the info, I figured it would help).
Gained a sub by the way
Hi, it's interesting, as someone else reached out to me last week with a very similar question, and what I think is the same model water heater. Therefore, I'm going to repost the response I gave them. (however, the short answer is: Always check with the manufacturer's instructions!):
It's difficult for me to assess your situation. Traditional check valves are usually noticeable by following the water lines and looking for them that way. Some recirculation pumps have built-in check valves which may be hidden in the pump's outlet. Your best bet is probably to check your unit's and equipment's owner's manual, to get a clearer idea of the requirements. The bottom line is that if the heating water is getting trapped in any way (there is no avenue for expansion), then you will need an expansion tank to accommodate the expansion. Some signs might be intermittently-leaking temperature & pressure relief valves, as I demonstrated in this Short:
ruclips.net/video/pGCPExUvxLs/видео.htmlsi=vLhq8Wx_vt0PVUfn
Hope this helps!
Awesome! Thanks for your time!
We installed an electric tankless water heater for a bathroom in a metal building. when we turn on the hot water , it spits and surges for several minutes and then runs normally. Is there anything we can do to get rid of that issue?
Hmmm...that's a tricky one without assessing directly on site. I will say though, if it takes several minutes to for the spitting an surging to pass, I doubt it has anything to do with thermal expansion, as the pressure relieved from thermal expansion is rather instantaneous from the moment you open the tap. The way you describe it, it sounds like a classic case of air in the lines...although air will not typically simply "appear" without a water shutdown, thereby allowing the opportunity for water to enter the system via an open orifice, such as a hose bibb or faucet. But again, I can't tell if it is air without being present. I'm wondering if your electric tankless heater has some sort of flow restrictor or device, which may be malfunctioning. I know that once in a very rare while, my tankless gas heater acts up and causes the water to run restrictedly while emitting a terrifying hammering. I simply unplug it, and plug it back in, and the phenomenon disappears.
How d you winterize an expansion tank?
Interesting question. In the event that you DO need to winterize your system, then that would mean that you're draining down your system of any excess water. In that case, as long as the expansion tank is not isolated from the rest of the system when you drain it down, then any residual water should be "pushed" out of the tank while you're draining - leaving only air in the tank (which is not subject to freezing). Ensure that any water lines in the building are not trapping water, which may freeze and lead to frost damage. Also, If your expansion tank is installed sideways or upside down, you may want to consider outright unscrewing it from the fitting and draining the tank manually of any trapped water by flipping it with the inlet side down...only be sure to re-T-tape the thread and reinstall the tank BEFORE you turn the water back on! 💦 Hope this helps.
On a normal system with tank isn't it more or less SOP to place the expansion tank on the supply (cold) line? Ergo your video with the expansion tank placed on the hot line might be a bit confusing to the novice.
I don't recall offhand specifically what I said in the video, though I would reason that it would be equally acceptable to me place it on either the hot or cold line (presuming the absence of any check valves in between). I prefer installation on the cold side if applicable, because doing so would likely delay failure of the air bladder. However, these are certainly rated for hot water (as is typical in a hydronics system).
Doesn't the expansion tank go on the cold water line?
I prefer the tank to be installed on the cold side, only because I presume that the temperature rise on the hot side may cause the bladder to fail prematurely. That said, it's still perfectly acceptable to install on the hot side, as they are nonethess designed for higher temperatures (such as part of a radiant floor heating system); only my preference.
The important thing above all, is that whichever side you install it on, is that it's downstream of (past) any check valves, which will block the water from expanding.
why do you install a check valve on the cold
A valid question! Note that you don't ALWAYS need to install a check valve. In certain circumstances when measures need to be taken to eliminate the possibility of water reversing toward the source water supply (otherwise known as "backflow") in the event of pressure differentials caused by various reasons.
In this case, the check valves were already existing, and my suspicion is that the purpose of this particular cold-side check valve is to eliminate or minimize the creep of hot water rising up from the tank, back up into the cold (for thermal efficiency). Although it's arguable whether a check valve would be needed at all in this particular scenario (I see absolutely ZERO need for one on the hot side), this is an extremely large home with tons of concealed piping, four(!) independent domestic hot water systems and respective recirculation lines, I felt it best to err on the side of caution and keep the check valves by simply install the expansion tank to resolve the issue, rather than blindly eliminate the check valves without the ability to deduce the repercussions. Note that a check valve IS necessary on the hot water recirculation line just upstream of it tying back into the cold water supply upstream of the tank, because failing to add one will likely cause cold water to backflow up through the recirculation line whenever someone opens a hot water tap (thereby causing the cold to mix with the hot).
As well, sometimes the municipality, township or other conditions require the installation of a backflow preventer (which is really a testable set of check valves in series) on the cold water feed coming into the building (particularly if there is a risk or possibility of the potable water supply becoming cross-contaminated by harmful chemical which may exist or be used within the building.) The installation of a check valve or backflow preventer will instantly create a closed system because the water downstream of the device has nowhere to go. Therefore, an expansion tank is absolutely necessary.
Hope this helps, and thanks for your inquiry!
never seen cold water comes in on the left of a tank?
Neither have I! 😁 Only laid them out that way in the illustration to avoid the pipes crossing over for sake of clarity. But at least I drew the faucet lines accurately...which is actually a requirement by Code.
Can I call u for consultation
Hi there! Unfortunately, I don't typically do one-on-one consultations.
Please feel free to share your challenge or concern and we'll see if we can help out!
l I forgot to tell you are Tankless is for hot water and heater
Hi. Here in south africa we use a thermal expansion valve to cope with this problem so then the thermal safety valve is the last safety device should all else fail.
Pressure reducing valve with strainer fitted to balanced cold and hot water outlets at 400 kpa.
Thanks for your feedback, and Happy 2024! I LOVE learning about the way things get done in other parts of the world.
I think what you're referring to is a pressure or temperature relief valve? If so, such valves are also typical and MANDATORY to be installed in all our water systems entailing the heating of water or liquid. However, a relief valve will NOT remedy the effects of thermal expansion; all it will do is prevent the system from building up pressure by allowing the increased pressure to escape via the relief valve.
An expansion tank is a completely different animal, as it takes advantage of the compressible capabilities of air (i.e., Boyle's Law). As pressure increases, the air's volume decreases proportionately, thus allowing room for the (incompressible) water to expand through the system.
(Hmmm....I think you've inspired me to make a video demonstrating thermal expansion. THANKS!)
Meanwhile, here's a Short demonstrating the effects of thermal expansion on a water heater, the role of the relief valve, and the installation of an expansion tank to permanently remedy the problem.
ruclips.net/user/shortspGCPExUvxLs?feature=share