Water pressing droping on combi bolier?

RaiderHammer

Hi I have water dropping below 1 bar in a combination boiler now on what seems a daily basis. Would this be a leaking pipe somewhere or could it be other issues? Bolier is a Saunier Duval Thema 23 combination bolier.

Looked around the pipes on view and on the radiators and can't see any leaks, also no noticeable leaks from the ceiling above.

Any ideas?

If the leak is under the pipework how do you go about spotting where it is? Measuring pressure at each radiator?

if you can't find the leak how can you sort this out?

Does Fernox Leak Sealer F4 work on combination boiler pipe work? Worth trying or will the issue come back soon even if this stuff cures it initially?

If there is an answer on this any idea on the rough cost of sorting the issue in anglia area?

Thanks.

keystone

Look at these two before you go looking for a leak:

1. Expansion Vessel.

There's a schrader (like on your car tyre) valve on the EV. Push on the pin. If air comes out then it may need repressurising. If water comes out the diaphragm is knackered and the EV needs replacing.

2. Pressure Release Valve

If the pressure has gone too high at some point (between 2½ an 3 bar) the PRV will have lifted to relieve the pressure. Once that happens inevitably carp gets in the seat and they don't reseat properly so they pass. On the outside wall behind the boiler there will be a length of 15mm copper pipe. That's where the water goes when the PRV lifts. If thats wet or dripping then the PRV is the source of your pressure loss. Forget F4 as a solution for this.

When was it last serviced? Repressurising the EV you can do yourself. Replacing it or the PRV requires someone with knowledge. ie - GALMI.

Cheers

RaiderHammer

I think the prv is in the garage I will check in the morning and get back to you. The pressure goes up to 3.25 when hot. Thanks.

keystone

RaiderHammer wrote: »

I think the prv is in the garage I will check in the morning and get back to you. The pressure goes up to 3.25 when hot. Thanks.

The PRV is in the boiler. The outlet will be on the other side of the wall from the boiler but unless the flue is discharging into the garage too I'm having difficulty envisaging that the PRV outlet is also in the garage. 3.25 bar when hot is too high. Thats your problem. The PRV keeps lifting to release the pressure so the pressure automatically falls. You are topping it up too high and have too much pressure in your system. It needs to be topped up when the system is cold and to no more than about 1 bar. Simples. Nevertheless you'll still have to get the PRV looked at because once its lifted once its almost certainly passing anyway.

Cheers

RaiderHammer

Thanks, the flue comes out above the garage roof and the PRV pipe is in the garage at floor level. I am guessing it's there because the old boiler was inside the garage but the new one is inside what was an old airing cupboard downstairs. I say new bolier but it's actually 10 years old.

I checked the prv pipe this morning and yes there is wet underneath it and in the pipe you can see / feel water. So that's my problem. I will call the engineer in. Fore warned is for armed so if anyone knows what the likely issues is that caused this can they let me know please. If you also know a rough cost of the likely repair, I would be most grateful. Thank you.

cloud_dog

RaiderHammer wrote: »

...so if anyone knows what the likely issues is that caused this can they let me know please.

Raider

Keystone has told you what the issue is. It is the extremely high pressure your boiler is going to when used which is the issue. You need to check what the pressure is when it is cold / not in use; should be about 1 bar.

We had a similar problem when I topped up the pressure in the boiler but the cold water feed valve (one of those screw driver jobbies) didn't quite seat properly when turned off and so very slowly continued to increase the (water) pressure in the system. I needed to replace the feed valve.

macman

Have you tried bleeding the rads to reduce the pressure?
If it's constantly going back up to 3.5 bar, (I'm not clear if you have been repressurising it yourself or not) then you have a leaking valve on the filling loop and it''s over-filling.

RaiderHammer

Hi Cloud Dog the pressure now when not in use is just under 1. I don't think it's filling up any more than what I put in. I have topped it up a couple of times when there's not been enough water in there for the boiler to work.

Hi Mac man Rads were bleed a couple of weeks ago when boiler was serviced. I have been adding the water myself. I don't think the gauge is going up any further than what I am putting in. I usually top it up to just a smidge over 1.

Thanks for all the help so far.

southcoastrgi

if it's 1 bar now & you are sure the filling loop is shut & the pressure goes upto 3 bar when the heating is on then it's the EV as KS said it either need re-pressurising or it's knackered, press the car type valve on it if you get air it needs pumping up if you get water it's knackered & will need replacing or an external one fitted on the ret as close to the boiler as poss

RaiderHammer

southcoastrgi wrote: »

if it's 1 bar now & you are sure the filling loop is shut & the pressure goes upto 3 bar when the heating is on then it's the EV as KS said it either need re-pressurising or it's knackered, press the car type valve on it if you get air it needs pumping up if you get water it's knackered & will need replacing or an external one fitted on the ret as close to the boiler as poss

I am assuming this is nothing I can do myself? I have no idea where this mis on the boiler.

southcoastrgi

the ev is on the left hand side however the MI aren't very good & i can't see if the front case is sealed & therefore part of the flue system, if it is then no you can't remove it to check the ev you will need a RGI, as it's a old boiler the case seals may need replacing after it's removed