Main 30 Eco - loses pressure in about one minute?

[Fez111]

Hi All,

I have tried searching for a fix for this problem before posting this, but was unable to find one in the forum. It's my first time on here, so i'm sorry if I've missed any forum etiquette. Maybe you can help?

I have a Main 30 Eco combi boiler that was installed about 2.5 years ago, and doesn't get used heavily - (only 2 adults and 1 child in four-bed house) so fairly new.

When it was installed I had all the central heating installed new too as refurb'd the whole house.

The boiler used to lose pressure after several months at first but progressively this has got more and more frequent. Within the last month or so it has gone from once or twice a day, to now lasting about a minute til it all drains away.

I have checked the PRV copper pipe and that seems fairly dry - no signs of dripping.

I have checked the radiators and none seem to be leaking.

None of the pipe work shows any leaks (though the kitchen pipe work is concealed in a wooden box underneath the wood flooring so not visible).

However I did check by closing the isolator valves and it still just drains away.

The water still runs clean at the taps.

I'm not averse to paying for a plumber to come and visit but the two I have had so far seem just as confused, so I was hoping you may be able to help?

One said we "could start by changing the domestic heat exchanger, and see if that does it, or then try something else" which didn't fill me with confidence. Another said that he'd try inserting food dye in the system to identify the source, but said that he wasn't sure either - hence my post.

Is there anything I can try to help identify or diagnose the problem - I have little knowledge of plumbing but can follow instructions! just want to know a little at least what I'm talking about before getting a THIRD plumber in.

Thanks you in advance for your help, I really appreciate it. Please ask if I have left anything out.

Fez

 

[bolshy]

Firstly, that's a lot of water to disappear without a trace. Tape a carrier bag on to the PRV pipe work outside, then top up your system from cold, with the flow and return isolators shut. These are the ones on the 22mm pipework. See if you collect any water in the bag.

 

[Fez111]

Thank you for the quick reply Bolshy.

If nothing else, the speed the water disappears makes it easy to test possibilities!

I taped a clear food bag to the prv copper pipe outside and filled the tank with the isolators shut.

The bag has come out empty, bar a couple of drops. (However the boiler wasn't fully cold though as was used just before the test - about 59c).

If it's relevant at all the boiler does make a loud groaning/whining sound when filling.

 

[toeknee8]

Hi Fez, Please let me know the outcome to your problem as I too have the exact same issue. I also have the same bolier as you. Odd dont you think?
Regards,
Tony

 

[bolshy]

What pressure are you filling to? Are you SURE it's the PRV pipe? With the correct flow and return isolators closed, there aren't many places left to leak to.
You say the boiler was in use? What is the pressure doing when the boiler is running?

 

[Fez111]

Tony - well if nothing else, It's heartening to know I'm not the only one with this random problem! I can live with the cold water, the irate wife is a different matter though! Lol

Bolshy - I am filling to about 2 - this is probably higher than it should be but has become force of habit after filling so often, and it going so quickly over the last few months. It doesn't let me fill above 2 anyway as what sounds like the air pressure (?) puts up resistance and then the filling stops.

FYI I just filled again and realised that when I closed the isolators really tight (tighter than before anyway) the rate at which it goes down slows down. Still going down but maybe every 10-15 mins rather than a minute if that makes sense?

 

[Fez111]

Also, yes def the prv pipe as I can follow the pipe from the pipe, to right out the wall, and then to the other side.

Before the first test, the boiler had been heating water for baby's bath. The pressure goes down constantly when boiler in use. The last plumber said to leave the filling loop open, but though I could tolerate the loud noise, I'm worried about the cr*p this may be introducing into a fairly new system - maybe I'm concerned unnecessarily? So only doing thus for bath time, since last couple of days.

 

[toeknee8]

Fez, You talk about isolator valves and the need to make sure they are tight. Which valves are these?. I am not a plumber but am keen to resolve this issue myself if possible!!

 

[Fez111]

Presuming same boiler Tony these are the two valves at the far left and far right at the bottom - attached to the slightly wider copper pipes ("22m").

 

[Fez111]

'22mm' even!

 

[toeknee8]

Hi Fez, Yes I have the exact same boiler as you. (Main combe eco30)
I have never touched the valves that you mention, however as it is late now and I dont want to wake my kids, I will have a look at it tomorrow after work and let you know if I get any joy. In the meantime, likewise if you have any joy please let me know. Maybe between us we get get the wives off our backs lol

 

[bolshy]

Make sure the boiler is turned off at the control switch. You need to shut the flow and return isolators properly. They should move a full quarter turn to be fully shut, handles at right angles to the valve bodies. If your boiler isn't isolated properly, you can't rule it out completely.
If nearly shutting the flow and return slowed the pressure drop though, and there's nothing from the PRV it sounds more like you've got a big leak under the floor somewhere. If you have to leave the filling loop open to keep up, that's a fair amount of water.
With the boiler off, quieten the house as much as possible, fill the system to as high a pressure as you can with the flow and return open, then isolate filling loop and try to listen for escaping water under the floor.

 

[Fez111]

Thanks for you help Bolshy. I have unbroken wood flooring running from the front door all the way through to the back garden door - it's a scary thought that I may have a leak that big underneath.

I will try as you say and feed back.

 

[Slugbabydotcom]

If it's definitely not coming out of the PRV and you cant see a leak then it's got to be coming out where you cant see it. Under the floor!
Look around the outside for damp areas. Is there a room where the windows always seems to steam up ?
Last time I came across one like this; the guy had just spent a fortune on expensive timber flooring and the idiots who fitted it had nailed a pipe while they were preparing the existing floor!

 

[toeknee8]

Hi Fez,
Any luck with resolving the water pressure issue? Do you know if a faulty diverter valve could lose the pressure? (diaphram probs)
Regards, Tony