Low water pressure in combi boilers

Which make of boiler are they Monica, because next time we replace it I shall remember the name? Thanks.

We have had combi boilers for 25 years and never come across this problem. We have 2 boilers and have had them both replaced so my experience is based on 4 boilers of this type.

I had to go up into our loft recently to add to the water pressure. I find I only have to do it annually and I always look on YouTube ,I simply add the name and model of my boiler and lots of simple videos come up to remind me which taps to move.
God bless YouTube I say.
Btw I do have an annual boiler service done by an approved heating engineer.
I agree with the original post though, it does seem to drop overnight, working fine one day,gone down the next day !!!

We have this problem sometimes and had to go into the loft to turn on the little taps that raise the pressure. Recently we paid a plumber to bring this feature downstairs into the airing cupboard. It cost about £100 but is so much more convenient than climbing the loft ladder. We used it twice over Christmas so it was worth it.

It does seem to happen a lot....to some boilers more than others, ours is an Ideal ( won’t have another one!)
There’s an internal cylinder which combines air and water, and sometimes the air pushes the water out.This then needs an engineer to clear the system out and rebalance it.
There could be a leak ( the other explanation) so check all the radiators.
DD has a combi boiler which she inherited with the house and is about 12 years old, no probs whatsoever.Ours is only 7 years old and we have this prob frequently.

‘That is how’ not ‘yet to how ‘ grrr

The expansion tank in a combo boiler is quite small yet to how it heats small amounts at a time that then feed to your heating system or to your hot water supply. Inside the tank is a diaphragm that when the heat in this small tank builds up will vent to an external point Sometimes the diaphragm will move too much to fully return to normal and so it will continue to vent at lower pressures. When the system cools down overnight the internal pressure naturally drops leaving less water in the tank than before any venting.

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.

We had our pressure valve replaced on ours a few weeks ago, similar problem.

Thankyou Teachername x

I do have low water pressure, the plumber mentioned it when he installed the boiler, but not too low as he still recommended the boiler and it’s been serviced every year.

I’ll have a think about the water pressure and discuss it when next serviced.

crazyH, there is a tap on the actual boiler, or possibly two taps, which you just turn to add water. They are somewhere on the incoming water pipes. If you have a display on your boiler, it will show you the water pressure gauge.

Have a look at the operating manual as there should be a labelled diagram of all the icons on the display and also where the taps are.

It’s worth knowing as it is an easy fix, but very annoying first thing in the morning!

I wouldn’t know where to start. I have a combi boiler, but how do you “add” water ? Where?

When I had my boiler replaced I would have liked a combi boiler for reasons of space, freeing up a large are of kitchen however my CH pipes were in the concrete floors so was told the increased water pressure would be too much for them.
I have lived to be grateful for that as two of my friends seem constantly to have the problem with the pressure dropping and frequently have a plumber visit as either can do it themselves.
I cannot answer your question, sorry , but just to say it seems a common problem.

I find that my boiler can go off in summer so it is definitely something to do with the pressure being up when the boiler is running. I know the water level drops more and more when the boiler isn't on.
Not much help but seems to happen to combi boilers as all my neighbours have the same issue.

Could it be to do with the pressure of your water supply rather than a problem with the boiler itself?

We have a combi boiler too but had ot replaced a couple of years ago. The old one used to lose pressure a lot. The current one doesn't.

So, in short, ?‍♀️