Low water pressure in combi boilers

I’m an old boiler who needs topping up with drinks AGA
So I can empathise with all other old boilers.

We had a boiler in a small flat that kept losing its water pressure while it was empty. As soon as it was lived in again, the problem righted itself. We had a couple of engineers round to look at it and they both said it can be a problem if the system isn’t run often enough.

We have this issue about once a month during the winter. We’ve had numerous engineers out and replacement parts and the consensus is we have a minute leak “somewhere”.

I had a lot of trouble with pressure dropping and the man who installed it told me it was a leak , but he couldn’t find it , he came back a few times , no joy . Usually SIL was the one to call him and stood gazing over his shoulder while he tested everything.
Last time it happened he and DD were away so I called the local plumber , he took off the cover and we gazed at the tiny fountain merrily spouting from a valve ne’er the top of the boiler . He replaced it and we have had no problem since ? fingers crossed ?!
It’s nearly always a leak in the boiler I’m told

To end this issue of waking to a chilly house, would it be better to check the pressure every week during the day or just prior to bed whilst you are dressed, comfy & able enough to get into the garage?
We check our boilers regularly and especially during winter they do occasionally need a top up. Both are modern less than five years old boilers.

A combi boiler is a sealed system; once its topped up with water, it just goes round and round through each radiator and back through the boiler.

I had a new Worcester Bosch boiler installed when I moved into this house almost 3 years ago. Within weeks the pressure kept dropping; I kept topping it up very couple of weeks, only for it to drop again. After 18 months of this, I discovered that there was a slow leak in the pipes leading to the hall radiator. Further investigations found another slow leak in the pipes to the kitchen radiator. Because the leaks were small (just drips really) they hadn't been noticed but were sufficient to lower the pressure in the boiler.

Try leaving a shallow tray under a different radiator each day, for 24 hours. If you find any water in it, you've got a leak.

25Avalon

Teacheranne I have the same problem but my boiler is in the loft - every few months I have to pull down the rickety ladder and struggle up there! I just turn the water valve on until the pressure is right and then turn it off.

I have asked the heating engineer what can be done as I’m not getting any younger to climb up there. Apparently it could be a slight leak in the system somewhere. We have checked all the radiators but no leaks. Suggest you do the same as it might solve the problem for you. It’s no joke when there’s no heating or hot water.

Thanks, I did check all the radiators this morning but they were all fine. I think I prefer traipsing out to the garage to climbing up a loft ladder!

trisher

Possible causes- you could have a tiny leak somehere you haven't seen. You can buy stuff you put in which seals these.
You may have air in the system- have you bled your radiators?
Your system may need cleaning there is stuff you put in the system which does this (think it's magnetic or something)
My DSs have done all of these for me at different times.

I’ll chat to the engineer at the annual service about any leaks in valves.
Radiators all checked this morning, no apparent leaks.
Boiler only five years old.
Radiators are bled annually at the service.
The system was cleaned out when the new boiler was fitted and I had something installed to keep it cleaned - no idea what it was though!
Could be low water pressure in the area, will ask my neighbours.

Luckily I know what to do, the two taps are easy to use and within a few seconds of adding water, the boiler came on again. It is inconvenient though especially in the winter so I thought I should try to investigate further.

A combi boiler is much cheaper to run though especially when there is only one person in the house using hot water, no great big tank to fill up!

Chewbacca

A combi boiler is a sealed system; once its topped up with water, it just goes round and round through each radiator and back through the boiler.

I had a new Worcester Bosch boiler installed when I moved into this house almost 3 years ago. Within weeks the pressure kept dropping; I kept topping it up very couple of weeks, only for it to drop again. After 18 months of this, I discovered that there was a slow leak in the pipes leading to the hall radiator. Further investigations found another slow leak in the pipes to the kitchen radiator. Because the leaks were small (just drips really) they hadn't been noticed but were sufficient to lower the pressure in the boiler.

Try leaving a shallow tray under a different radiator each day, for 24 hours. If you find any water in it, you've got a leak.

Good idea to try leaving a tray underneath radiators in case of small leaks, I’ll do that. As I can’t remember when I last added water to the system, I’m not sure that it can be a leak in a radiator but definitely worth trying it. Thanks for the suggestion.

Nonogran

To end this issue of waking to a chilly house, would it be better to check the pressure every week during the day or just prior to bed whilst you are dressed, comfy & able enough to get into the garage?
We check our boilers regularly and especially during winter they do occasionally need a top up. Both are modern less than five years old boilers.

To be honest, I could check the water pressure by looking at the WiFi thermostat controller in my hall, it gives a reading of the pressure but I’ve never thought to do that! I will now, thanks for the hint.

DiscoDancer1975

This happened to our daughter in a new build. We thought someone may have accidentally damaged a water main, as they were told this happens in combi boilers when the water pressure drops. They did something to get it working again, but don’t think it was adding water....more the twiddling of knobs! I got the feeling, from what she said, that this is a common ongoing sort of problem with this type of boiler.

Glad we stuck to our hot water tank, and emersion if there’s a problem with the boiler.

By twiddling the knobs, your daughter was adding water! It’s a case of knowing where the knobs are and which way to turn them!

I had something installed to keep it cleaned - no idea what it was though!

Your plumbing engineer has probably installed one of these on your boiler Teacheranne. The water that's going round the pipes in your house picks up all sorts of bits of rubbish that would normally just go straight into the boiler, stay there and clog it up. The filter has a magnet inside it that attracts all the bits of debris before it reaches your boiler - a bit like a sieve! When you have your boiler serviced, the plumber empties it out and replaces the internal filter paper with a new one. The amount of crap they catch is astonishing! Having one of these filters can extend the life of your boiler by a couple of years so well worth having.

I’m finding with our 6 year old Baxi , we never have that problem but previous ones in my old house , were terrible. Level would drop frequently. Ferroli combi was the worst and a real pain to sort out. It involved two taps underneath which were hard to get to.

air dissolved in water comes out and reduces the water pressure a bit. Pressure needs to be 1.5 bar or a tad under, don`t go too high or it could make pressure at joints too much, causing leaks

Chewbacca

^I had something installed to keep it cleaned - no idea what it was though!^

Your plumbing engineer has probably installed one of these on your boiler Teacheranne. The water that's going round the pipes in your house picks up all sorts of bits of rubbish that would normally just go straight into the boiler, stay there and clog it up. The filter has a magnet inside it that attracts all the bits of debris before it reaches your boiler - a bit like a sieve! When you have your boiler serviced, the plumber empties it out and replaces the internal filter paper with a new one. The amount of crap they catch is astonishing! Having one of these filters can extend the life of your boiler by a couple of years so well worth having.

Yes, that’s what it is! Thank you for reminding me.

karmalady

air dissolved in water comes out and reduces the water pressure a bit. Pressure needs to be 1.5 bar or a tad under, don`t go too high or it could make pressure at joints too much, causing leaks

My boiler has a red line to show maximum pressure so easy to know when to stop adding water.

Teacheranne

trisher

Possible causes- you could have a tiny leak somehere you haven't seen. You can buy stuff you put in which seals these.
You may have air in the system- have you bled your radiators?
Your system may need cleaning there is stuff you put in the system which does this (think it's magnetic or something)
My DSs have done all of these for me at different times.

I’ll chat to the engineer at the annual service about any leaks in valves.
Radiators all checked this morning, no apparent leaks.
Boiler only five years old.
Radiators are bled annually at the service.
The system was cleaned out when the new boiler was fitted and I had something installed to keep it cleaned - no idea what it was though!
Could be low water pressure in the area, will ask my neighbours.

Luckily I know what to do, the two taps are easy to use and within a few seconds of adding water, the boiler came on again. It is inconvenient though especially in the winter so I thought I should try to investigate further.

A combi boiler is much cheaper to run though especially when there is only one person in the house using hot water, no great big tank to fill up!

I have a combi here and in last house. Radiators do need bleeding if your heating has been off for some time, particularly if you have a large house. Air gets in (don't ask me how) You can sometimes tell if they need doing because they make noises when they come on and if there is a lot of air the tops don't get properly hot. It was always a problem in my 3 storey house when we put the heating on in the winter. I got quite good at it. Depends on your radiators how its done. Google it for instructions.