New Boiler - Pressure Dropping - No Visible Leaks

gazfocus

We have a house that we rent out and at the beginning of October, the boiler went and we had to have it replaced with a new one. We've now had a call from the tenant to say the boiler keeps dropping the pressure to the point where the boiler won't start (apparently this has been happening 2 or 3 times a week for a couple of months).

The plumber that fitted the boiler has been notified and he said it'll be a leak in one of the radiators but the tenant says she's bled all radiators and there are no leaks anywhere. There's also no leaks under or around the boiler that she can see.

The plumber is maintaining it has to be a leak somewhere so isn't willing to do anything, but this has only been happening since the new boiler was installed.

Can anyone suggest what it might be that's causing this?

WestonDave

If its that soon since the boiler was fitted, I'd be kicking the plumbers rear end and telling to at least do you the courtesy of having a look - or alternatively you'll get someone else out and in view of his lack of interest, bill him for anything that is found wrong with the boiler installation.


To be fair its not impossible that a new boiler might put pressure on old pipework and cause a leak but you'd expect to see it somewhere if its dropping at that rate.

Wookey

Is this a gas/oil boiler with instant hot water or indirect (stored) hot water? if it is stored and there is defo no leak in any of the heating pipework there could be a leak in the hot water storage cyclinder, this can be noticed by discolouration in the hot water but is usually so small that it's barely noticeable.

The only other explanation is that the pressure release valve isn't holding the pressure or the expansion vessel, top up the system to pressure and then run the boiler up to temp and watch for water coming out the boiler pressure valve discharge pipe, there may also be one from a tundish at any hot water storage tank.

Crinkmeister

You could do a check to find out if either the boiler or heating circuit had a leak, but that would require you to not run the heating for a few days. Not really practical at the moment. My money is on a leaking rad. They don't have to leak much to drop the pressure and it can be difficult to spot when the heating is on as the leaked water evaporates.

J_B

gazfocus wrote: »

but the tenant says she's bled all radiators and there are no leaks anywhere.

Crinkmeister wrote: »

My money is on a leaking rad. They don't have to leak much to drop the pressure and it can be difficult to spot when the heating is on as the leaked water evaporates.

Could it be possible that she hasn't tightened the rad bleed screw back up tight enough?

That besides, any decent plumber would be back to 'look see'.

Apodemus

Is it possible that the system is one where you need to recharge the system manually after bleeding the radiators? I've seen one that was quite temperamental but solved by recharging back up to full pressure.

Apodemus

J_B wrote: »

That besides, any decent plumber would be back to 'look see'.

You would think so, but sadly there seems to be a trend towards "installation only" heating engineers who are happy to take the large mark-up on a quick, easy, comfortable job but won't touch the lower return, greater hassle of the routine servicing and repairs jobs.

Ectophile

A couple of thoughts:

There could be a leak under the floors, where no-one can see it.

There could be a leak from the pressure relief valve, which usually vents to the outside. This is not the same as the condensate pipe, which is meant to drip.

Alias_Omega

Pressurise boiler and isolate it. If fault is not present, it's in the system. Check PRV valve is not leaking, try a bag over outlet. If you have pipes in concrete floor, it could be that. Lift floorboards, inspect... Must be going somewhere!!

ComicGeek

My money is on it being a pressurised system, and that the tenant has bleed the radiators causing the pressure to drop and hasn't refilled the system to compensate. Even if you've taken a small amount of water out of every radiator this will be enough. The replacement of the boiler will likely have left air in the system, so the tenant probably had to bleed some rads a lot.

If it previously had a cold water tank in the loft and this was replaced with a pressurised system when the boiler was replaced, then it could be a leak somewhere - in this case the plumber should have been frank about the risk of leaks in the system.

But my money is on pressure loss due to radiator bleeding and not refilling. The OP hasn't mentioned whether they have tried refilling the system.

Lorian

Expansion vessel has not been pumped up?