Why Your Boiler is Losing Pressure and How to Fix It
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- Опубликовано: 9 май 2024
- One of the most common problems with central heating systems is continued loss of pressure requiring the owner to refill the system more often than they should. Here we look at the common reasons this happens and what you can do about it.
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I’m a heating engineer and I often watch videos like this behind my hands like watching a horror movie 🫣 but I’ve got to say, fair play my mate, your explanation was spot on, to the point and made a lot of sense 👍🏻 although opening your PRV to show it coming out outside was a risky move, they have a habit of never fully closing once being opened.
Also another reason for pressure drop can be people (DIYers) not understanding the difference between single and double barrier push fit pipe. I’ve seen it before where single barrier pipe has been used and what this does, is allow the oxygen and hydrogen in the water escape through microscopic holes in the pipe wall, without any signs at all.
Great video pal
Great video Stuart. This will possibly save some folk a bit of cash.
Love the references to various laws:
Charles's Law: When the pressure on a sample of a dry gas is held constant, the Kelvin temperature and the volume will be in direct proportion
Boyle's Law: The absolute pressure exerted by a given mass of an ideal gas is inversely proportional to the volume it occupies if the temperature and amount of gas remain unchanged within a closed system.
Coles Law: Thinly sliced cabbage
I've had exactly this problem in the bungalow that we converted for my disabled brother. It had a new heating system and new combi boiler installed, and all was well for a year or so, then it kept losing pressure when the central heating was used. It went from needing re-pressurising every few months to every couple of days. The problems were essentially all down to the installation. Most importantly, the plumber had not installed automatic air vents in the system. Being a bungalow with a solid floor, the plumbing went through the loft, and was one set of inverted loops. Any gas would accumulate in the pipes at the top, and gas expands more than water when heated, that pushed the pressure over 3 bar when the central heating worked hard, pushed coolant out the pressure relief valve and the problem got worse. This was made worse by insufficient inhibitor. Further, the system contains a lot of water, and the expansion vessels in modern combis are relatively small and the pressure goes up markedly on big systems when the central heating works hard.
So, having had a fruitless chase for leaks, I ended up installing a couple of automatic vent valves in high points on the system, a supplementary expansion vessel to give a bit more stability to the pressure when the system is heated up, installed a magnetic filter, which is also a good place to put in additives on a combi system, and dosed it well with inhibitor.
Now it seems to be very stable, and the pressure fluctuates less than half a bar between when it's cold and when the central heating is up to full temperature.
Now in my spare time I'm working on a little project to use a microprocessor and pressure sensor which I can monitor remotely over the Internet with an email warning system if pressure gets low. I'd rather have a log of what the system is doing and deal with it at the right time than an emergency call when the heating has broken and a 70 mile round trip for a 2 minute job. Nobody seems to sell such a system, and I would have thought it of great benefit to anybody who has something like holiday properties that they rent out. Perhaps there are some "smart" boilers that can do this sort of stuff.
Another lesson is don't assume plumbers and heating engineers always do their jobs properly.
nb. what is coming out of your boiler vent is most certainly not smoke (if it is, then it is time to call the fire brigade). What you are seeing is condensing water vapour, something entirely different and what what clouds are made of. To maximise boiler efficiency, then you actually want as little of that to appear as possible; you want the condensing to happen inside the boiler as that is where the maximum heat is extracted. Condensing boilers are at their most efficient with a hot water temperature of about 55 Celsius, so to save a bit of gas, try turning down your boiler temperature if your radiators are large enough. If you install new radiators, make then big ones as the heat pumps we are told we will have to use in the future work at around 50C, not the 80C that many boilers are set to.
I would also add, if you are checking for water coming out of the pressure relief valve, don't mistake that for the condensation outlet pipe. The latter should always be producing water when the boiler is working, although it is generally in plastic, not copper.
Great video! A couple of handy hints relating to pressure loss. First, a plastic bag tied over the end of the pipe from the pressure relief valve is an easy way of determining if water is escaping. The pipes are often angled back towards the wall to prevent scalding, so putting a tray underneath isn't always possible. And second, if the internal expansion vessel is at fault, rather than have the boiler dismantled and a branded replacement vessel put in, simply ignore the faulty one and have a cheap generic (Screwfix or whatever) external vessel added elsewhere in the system at a convenient point. Much cheaper and far easier to subsequently replace if it fails again.
I came home Saturday morning to discover my boiler off and displaying a low pressure fault code. True enough the gauge was almost at zero. Ten minutes doing a bit of refilling via the loop and bam, I'm up and running again. It's only happened twice in four years and then only when we have a sudden cold snap - I'm calling that 'normal'. Great vid sir.
I am going to wait a bit longer,maybe you are wrong and it fixes itself 😂
That's always the hope but it never does sadly. Always better to get it sorted (if you can afford it now) early before the whole boiler goes and it becomes 10x more expensive.
We kept it down to 10 minute bursts of heating when needed and shut it off before it got past 2.5 bar until we could get a plumber in
😂😂😂😂😂😂
It worked for the oil leak on my motorbike. Clever bike.
Love your videos . I’m a plumbing enthusiast and love to know how the main components I depend on work in my house . Thank you , you are one of my favourite RUclipsr with detailed information even a layman like me can understand.
Excellent advice, and I'm the son of a retired Plumber and Gas Engineer
Thanks for this video, my boiler has been losing pressure for a while now, after I watched your vid, I suspected it was the expansion vessel. Had to get a plumber out to recharge it, but was good to have a bit of information prior to the plumber coming out. He was nice enough to show me exactly what had gone wrong and explained it pretty much like you have in your video. thanks again!
So helpful--I'm new to the UK and I have a new combi boiler which I didn't understand at all. Now I feel more comfortable with it and a lot smarter! Thank you.
Brilliant and the timing could not be better, thank you
Just replaced our old expansion vessel. Been leaking for too long. Finally got round to it. Great video!
Thanks Stuart for some well explained and useful information. And thanks for the heads up last week on the Screwfix/DeWalt drill deal. I'd been after a couple of 5ah batteries for a while. Screwfix sell them for £80 each (I know that I can get them a little cheaper elsewhere) therefore two would be £160. So for £10 less not only did I get the two batteries, I also got another charger, a case and a combi-drill. Result!👍😁 Thanks again.
Thank you proper DIY. Very informative and just what I was looking for my sisters CH system loosing pressure.
Great video. Thank you for the tips. This was me earlier this year. But I had a fualt in a weld on a part of the boiler, then water came gushing through my ceiling.
Very nice video as always! Interestingly my boiler lost a lot of water last year (had to fill it up every two weeks or so), but it seems completely fine now! Over the summer, the boiler has been on "summer mode" i.e. running only the water heater, without any loss of water. And now that I'veturned it back into winter mode for the central heating... everything is fine! The problem seems to somehow have cured itself over the summer. Very confusing.
Coming from someone like yourself I found this video really easy to understand because I was thinking the same way as you & not like the expert who we can't do without but doesn't like to give us DIY people to much information so well done again on your explanation to things around the home.
These videos always leave vital snippets of info out.
Best to keep things diy friendly. Deep dives could put people in troubled waters.
Nice well explained video. Just to say though that the 'plume' that can be seen coming out of the flue of a gas boiler, especially in cold weather, is normally just steam. If for any reason it appears to be (and might smell) like actual smoke or something burning then switch the boiler off immediately and call a heating engineer.
Weirdly this is a problem one of my clients mentioned to me today but I’m going to leave it to a certified plumber ( which I am not ) very interesting all the same , excellent advice as always Stuart 👍👍
Hi Stuart, Good advice, great video👍
Very informative video, Stuart. Appreciate it, cheers.
Thank you so much for this clear and helpful video, it's been very useful.
Very informative, Thankyou.
Nice explanation Stuart, as you said, I'll leave it to the professionals ;) One thing does deviate over here in belgium, our safety goes into a drain inside the house, not outside. A bit harder to check if it's releasing water, can't put anything underneath it. But our set up is only 2 years old, after having the issues you just mentionned :D A broken internal expansion vessel in the boiler resulted in a pumber installing an external one and twe years later we replaced the entire boiler. As a DIY'er it's annoying when you can't fix something yourself, isn't it :D
I don't have a boiler, and doubt I ever will... but I still find it fascinating to watch you explain this (and many other subjects I don't have a need to know about). You are a great teacher and entertainer!
You live in a hot country ?
Great video, explanation, and as ever, thanks for sharing 👍 😊
Thanks, a great explanation of what is going on.
Roger B from the skill builder channel suggested a great way of finding a seeping leak. Put after shave in the system. Where the clean smell is the dirty problem is hiding
Lots of useful comments below. Its like our local plumber's merchant (dedicated store), if you have a problem, chew it over with the staff & whoever's in the shop, and someone will have an answer. Nice vid, thanks.
Nicely explained! 👍😃
Thank you again for a great video
Very spooky that you put this video up today as I have a leak detection specialist here today looking for a leak in my system. This has been going on for 6 weeks, I have had to top up my boiler pressure every day for 6 weeks. I've had 4 visits from British gas who have checked my boiler and eventually they replaced the heat exchanger which I don't believe needed doing. Eventually they said it must be a leak under the floor. So I had to wait another 3 weeks for the leak detection man to come. He used his fancy smelling machine with no luck so started taking up the floors, on the third room he found a leaking push fit coupling. He has fixed it and hopefully it won't drop pressure over night. I'll update you tomorrow.
@davidsecker5161 How did you find the "leak detection specialist", please? I have a very similar issue and could do with a contact.
@@BimBim-_ I have british gas homecare and they sorted it. Good job they did as when the chap came he told me his company charge £800 a day.
Great explanation Stuart. Just had this issue with my Worcester combi. Kept losing pressure because it was dumping out the release valve. Plumber replaced the expansion vessel last week along with a service which set me back £390 +VAT 🤑 Pretty handy DIYer but hands were tied with it being inside the boiler!
You can add your own external expansion vessel in that case and leave the failed one in the boiler as is. Of course you need somewhere in the system to install such an expansion vessel, but it doesn't have to be close to the boiler. Pressurising them is easy. They normally have a car type valve at the tope and a bicycle pump and gauge will suffice.
@@TheEulerIDThe expansion vessels come ready charged. If you want to check or re-pressurise one on your heating system you have to release the pressure in the heating circuit, by either draining your system or, in the case of an inbuilt vessel, isolate and drain the water from the boiler before checking.
I got gas boiler in sept and needed topped up every 36 hrs. They came and took a release valve out that the oil system had used and now 6 weeks passed and I had to top up again, and then 2 weeks later, brings me to today. I asked a random plumber who was in my work doing a rad and he explained this expansion issue and said as I've 5 bedroom house I would prob need a separate expansion vessel and to hang a cup on the outlet outside, so that's the stage I'm at, but was wondering if that's the norm but as your covering it in this great vid, I see truth in what he said. We fou d no obvious leaks BTW.
Good video Stuart. For the pedants like me, adding a circulator to the diagram might have been useful for those not familiar with the essence of the mechanism. But I appreciate that you probably didn't want to clog up the diagram.
And a plumber impressed on me to never call it a "pump" neither! :-)
They are pumps; circulating pumps. On combi systems they will be within the boiler itself.
Presented wonderfully
Great explanation and nice demo of expansion. I think keeping the heating always on (rather than on timed bursts) will help limit expansion as the temp range of the water will fluctuate less. I am a big fan of running at a bit lower temp but always on.
God knows what my energy bills would be if I kept the heat on all night 😲
@@tttt4029, the thermostat turns the energy off once you reach a set temp and back on when you go below. Keeping a well insulated house at constant temp (e.g. 18C) is not as expensive as you think because the house doesn't ever get cold.
@@frankief7111 I do understand how a thermostat works 😁. The point is 18c is too low as I have children in the house and I dont live in a particularly well insulated house. Otherwise, I would agree it's feasible 😁
Great video cheers Stuart, is there a chance of a video for radiator removal for sludge, with advice and tools needed .
Very interesting and helpful video, 👍
very useful as always. Thanks
Thanks Stuart, a useful overview, I think we've had most of these issues one way or another over the years so this would have been handy to know 20+ years ago ! Still is now of course !
I will be interested to see what the comments say in response to this, Roger on the Skill Builder channel has been covering some of these issues over time too !
Sometimes with the slow release of water problem, just stick a balloon over the prv outlet outside, this works specially if the pressure s over say a week or two and will pick up small drips as opposed to a tray.
I learnt some of this from my plumber recently. I was having to top up regularly and noticed when I did, the pressure would rise very high when it switched on. It then started to leak from inside the boiler (not to a drain), so I was just getting water coming out of the bottom of the boiler.
It turned out this was the pressure release valve. I'm my case, the membrane hadn't failed, but the vessel was still being fully taken up by water (I guess the membrane in my boiler is very flexible). The plumber pumped up the air pressure behind the membrane and set the water pressure to 1bar. He said if there was an air leak on the air side of the membrane it would happen again - then he can take another more costly look (in the case it could be a damaged membrane or a faulty valve), but I think in this case the air just very slowly escaped from the air side over time, as it has held the same 1bar pressure for 3 months now.
Part of the issue was possibly due to when I was topping it up over the last 10 years, I was putting more pressure in than I should have been, which would have put more pressure on the membrane long term. This video helped me more fully understand what was going on - so thanks for that.
This happens to my boiler but only over the winter months I probably top it up once maybe twice a month between November and February, rest of the year it’s fine. No leaks anywhere I can find. Also I check the pipe outside and it looks dry, never thought of the air vents though. Good video 👍🏻
On very important thing is that, with sealed systems, if you have pipework above the radiators, then you need an automatic air bleed valve at the high point, otherwise air will remain trapped there. That often happens in bungalows with solid floors where the pipework runs up through the loft. The air in the system expands much more rapidly with temperature than does the water and if you get very large pressure fluctuations between when the system is hot and when it is cold, then that can be a cause (the other one is a failed expansion vessel).
I have just gone through this exercise with my disabled brother's converted bungalow. The installers had not put in automatic air vents in the high points in the system. If the high points in the system are radiators, then you can get automatic bleed valves for those which I recommend. In a combi system, you want the trapped air out as soon as possible before it starts pushing out the coolant via the pressure relief valve. If you find you have to bleed radiators of air, then they can be a good investment (about £20 for two from outfits like Screwfix).
Really useful, thanks
Condenser boilers don't emit smoke, it's CO2 and water vapour.
Well, the bit you see is water droplets - that vapour condenses (hence the name) and is therefore a cloud, or fog…
Very informative, even though I now have (the pleasure of) a Daikin Altherma heatpump :(
I knew almost everything you talked about... But I did not know the air in rads could be hydrogen gas... I learned something new today... Better not smoke whilst bleeding the rads I guess😅
Years ago, I had a Potterton boiler, great & economical when it worked, but the most unreliable piece of equipment ever (and after sales service non existent). Always slowly losing pressure, & after YEARS of trying everything, I found that the body of the alloy heat exchanger was seeping water when it got hot. As it slowly leaked, being hot, the water evaporated, hence I could NOT find the leak. In desperation, I fired it up with the covers off (!!), and sure enough, after 30 seconds or so, I could see it weeping. Vaillant from now on.
Fantastic explanation! I have a question. If you were to tap the expansion tank, would it make a different sound depending on where you tap it? For example, would tapping the top (air side) sound different from tapping the bottom (water side)? If the expansion tank is full it would sound the same or does the pressure in the tank prevent this kind of test from being reliable?
Hi Stuart, do you fancy embarking on insulating and framing the walls in the workshop please? I'd like to do it but can't find any good resources, we have the same garage and I know you'd do a Proper job!
Could you do a video of installing hive system to a combi boiler?
One tip you missed is check for a leaky schrader air valve on the PV - Have encountered just such a case where the insert refused to seat properly, was jammed solid and so could not be extracted and replaced - The solution was a cheap valve extender with it's own schrader valve (usually sold for bikes etc) screwed over the original, still working a treat 5 years later...
I had a new combi boiler. Since then i have 2 problems. Loss of pressure and water hammer sound. And also i hear dripping water in the walls wher the pipes located. Please advise
Brilliant stuff. My boiler needs to be topped up every two weeksand our regular plumber is retired. I know its a fault and needs fixing but how do you go about getting a plumber you can trust?
Ask a neighbour for recommendations?
@@ice4142 I've tried the local booklet that recomends trades people but no luck. I called out the makers (Worcester) for a service last time and they charged me £170. That's a lot for this old age pensioner but thanks anyway.
I had a brand new boiler fitted by cowboys in 2019. Worked a few times but since 2020, I haven't been able to get it to work. I've drained the whole system now and I want the WHOLE LOT ripped out. I use electric oil filled radiators now and it is far cheaper. How much to have the whole GCH ripped out completely?
I have a Junkers combi boiler that loses pressure constantly. I have to top it up every single day, sometimes more then once a day. There's no leaks, the expansion vessel is new, but the pressure keeps falling down really quickly when i open the hot water on the sink. After i turn the hot water off, the pressure goes up, but not to the point it was, before i opened the hot water tap. Is it possible that the 3 way valve is defective and needs changing?
8:56 "when the system is off" --> does this mean system completely off with the emergency toggle switch off, right?
How dare you! My boiler may be old, but the pressure is fine, (the missus says every old boiler loses pressure from time to time, it is nothing to be embarrassed about), and I don't need a new bleeding radiator. 🤣🤣🤣 Great video, in the US of A most modern houses have central air heating and cooling, although some houses especially in the North East and Mid-West have boilers with steam heat radiators.
One possible other problem with expansion vessels is the pressurisation vessel valve - basically a tyre valve - which can go. You can get valves that screw over the top of the faulty valve that sorts this problem allowing it to be repressurised. Although a simple fix, not a DIY one as you need a plumber to do this job properly within the boiler.
Help! My 22 year old conventional Valiant (non condensing type) boiler is loosing pressure. Bleed all 6 rads. No air. If I let the pressure drop to zero, when off, the boiler fires up perfectly & the gauge rises to about 1.5 bar. Plenty hot water & radiators about 62 C. No evidence of leaks from upstairs two radiators downstairs have pipes under floor. I have a hot water tank & cold storage in the loft. Boiler external pipe shows no leaks. What can this be?
I had an issue with my boiler losing pressure.long story short. I had replaced carpet in my hallway with laminate flooring. The additional pressure on the floor highlighted a flooring nail that had been put through a pipe. It must have been in there for years.
If its a Worcester Greenstar it is probably a cracked heat exchanger if you are topping up every other day, especially if you see the flue output looking like the Flying Scotsman at 80MPH !
I thought you said at the start you're were going to explain why the pressure still goes down over a year even when there is no fault, but perhaps I missed that bit or didn't understand it properly?
It's something that's always baffled me when I have to recharge the boiler once or twice a year, where has that water from the closed system gradually gone? You confirmed once or twice is year is completely normal, so what's happening in this normal situation?
I have a Worcester Boche green star the gage was losing pressure I had a plumber under the floor boards and no leeks to cut a long story short the valve cense was not working correctly and I had the hole system flushed and new censer fitted ££ at the moment everything looks okay
What causes air Ingres where the pressure only drops after bleeding? I have my Combi system dosed up with x100 inhibitors which test as the right strength. I am having to bleed the towel rail every two weeks despite a recent new boiler being fitted.
Is your pipework copper or plastic? If it’s plastic, is it grey?
My boiler went from 1.9 to 1.7 bar in 10 months. Not worried at all! Especially as the expansion vessel is in a place that is some 10 degrees coller now compared to then. Which accounts for nearly 1 bar difference by itself.
I put a hole in a plastic pipe.. Is that fixable yourself or one for the plumber?
I managed to fix it myself but not sure it's a long term fix..
Just cut it and fit a coupling.
Oddly I get what looks like the SRV overflowing only when the hot water is being heated. Not when the heating is running and I’m not losing pressure. Does the hot water cylinder have an expansion tank too?
My ecoking boiler leaked at the heat exchanger from day 1, took 5 years for plumber to find it, luckily just before warranty ran out, naturally ecoking didst want to cover it but after a fight they did send a replacement which was updated in the area mine leaked, go figure.
Check the shader valve for water or air
Any suggestions to why, when running hot water, it decides to run cold and takes around 30secs to get hot again? I have a regularly serviced combi boiler.
(Hi I am a plumber btw lol) Yes, sounds to me like it’s your secondary heat exchanger is clogged up. I bet the water gets very hot before it goes cold does it? Can I also guess that it’s a baxi boiler?
It’s a very common problem on boilers and any plumber worth his salt should be an easy fix.
Thanks for the comment. The water doesn't get extremely hot before going cold but you are correct in identifying it being a Baxi!
Can I show off and guess it’s a 105HE? I’m pushing my luck now lol I still think it’s your secondary heat exchanger tho, but it is hard with out being at the boiler
Its a Platinum combi boiler HE, its about 12 years old.
When the opposite happens and the pressure keeps climbing before the PRV lifts it can be a leaking filling loop.
This is so weird, literally been having this issue in the last week 👀
Is your Flue installed incorrectly? I thought none of the white section shouldn't be on show?
Sometimes the PRV leak plus the EV might need need re pressuring.
Iv just pumped my expansion up as it has been going to 0 good one
Another issue can be the sensor that measures system pressure can fail, making the boiler shut down, because it does not think there is enough water in the system. A faulty sensor is an irritating and expensive call out to a service engineer.
Cracked heat exchanger will cause the same problem with no evidence because the water is being vaporised in the burn, happened with my Ideal Logic and the warranty engineer said it was very common.
Sometimes water escaping from the PRV can be a faulty PRV itself passing water and not a faulty expansion vessel.
Water pressure needs topping up every couple of months,now i only have C/H,but no hot water
its always TRV valves on rads
Don't be isolating the flow and return valves because you've watched this video and think it's helpful.. don't be changing an external expansion because you've watched this video and think it's helpful
I've 20+ years in the trade and it can easily become a recipe for disaster..
Takes 2 mins walking into someone's house to see that mr DIY has had a go himself and completely balls it up coz he watched a you tube video
What is the opposite? Pressure too high. Overflow dripping.
If a Combi, check the expansion vessel. What pressure you showing.
@@tazmaniachill I'm having that issue - goes up to 3 bar when heating on - so drips a bit via overflow - not much but eventually dips below 1 bar when off so have to top up sometimes.
@webbo73 expansion vessel has ruptured, and is now probably full of water (a shown in the vid) if its not a combi boiler, you will still most likely have one in airing cupboard or near where the boiler is mounted if you have a sealed system. If your showing just under 3bar, that's teetering just at the limit of the prv (pressure relief valve and why its dripping) if it triggers, it sounds a bit like a machine gun going off. 😀 as it expels the extra pressure. Sealed systems are usually 1 to 1.5 bar, the expansion vessel should be pressurised the same to equalise as the water heats up. You probably need a plumber 👍🏻
P.S. if you have an external expansion vessel, look at the top, their will be a cap which you can unscrew and you will see a shcraeder valve (like what pump up a tyre) very gently press the valve down, if you get water coming out, then you need a new expansion vessel. If yours is Inside the boiler get a plumber in anyways 👍🏻
@@tazmaniachill thanks for the info! It is a combi boiler with no external vessel. Sounds like I need to get the old cheque book out 🤣
@@webbo73 most likely, depending on the make of the boiler, you might be lucky and the expansion vessel might be on the side of the boiler casing left or rhs. But then again some manufacturers put them in the back and impossible to replace, it's easier just to Install and external one and ignore the supplied built in one. Good luck 👍🏻
You don't need to be a qualified gas engineer. you need the be 'competent'. However if it takes the side of the house out you'll have no insurance!
Incase you don't know aluminum is metal.
Or just get a bicycle pump easy diy job 1bar
Well they asked why is your boiler loosing pressure??? Because it is fucked
😂😂
Rename this video "how to bleed a radiator" thats the only help it gives