PRESSURE LOSS

[jerryl]

Hi Guys
New to this forum and I have logged on in desperation. I have a pressurised CH system which is run by a Potterton Prima F Boiler. I am losing pressure on the CH really quickly. I have filled the system on the loop up to 1.5 bar and the CH heating works fine. There is a vent value in the airing cupboard that I have let all the air through and the radiators are also empty of air. The pressure never rises when the water gets hot and after about two to three hours the pressure gradually drops to 0.4 bar and then the boiler and pipes start to bang and then the system cuts out. I have checked and there is no water dripping from the PRV to the outside overflow. Any ideas, can't find any leaks on the rads, I haven't checked under groundfloor floorboards as yet, could it be anything to do with the expansion vessel? PLEASE HELP MY KIDS ARE GETTING COLD

 

[kevplumb]

the pressure never rises (nuts )

the pressure drops you have a leak bonny lad

 

[jerryl]

Can't seem to detect a leak anywhere any other suggestions.

 

[Strachan]

Do you use the boiler to heat your water via a coil through a cylinder?

 

[jerryl]

Yes I do use boiler to heat water, the cylinder is brand new it's a Hercal G3 with 148 litres capacity.

 

[Blasphemous]

Can't seem to detect a leak anywhere any other suggestions.

A Leak on upstairs Rads normally at some point shows itself by water marks on the ceiling below. A leak under the floor downstairs however is much harder to spot because the leak, leaks into the ground.

I agree with Kev... its leaking somewhere mate and my bet is under the floorboards downstairs. Take a few up somewhere easy to get to (big enough to get yourself under the floor). Have a look around down there. You'll need a torch! Have a look for any 'Green' areas on the pipework. That can be a tell tale sign but if its a newish leak then there might not be any signs of leakage just yet.

When you're under there be careful of the Boggie Man

 

[jerryl]

Should there be large amounts of water considering how quickly the pressure drops?

 

[ChrisR]

If the expansion vessel is full of water then , though you would expect a pressure rise when the CH warms up, you wouldn't need to lose much water to lose all the pressure. So check that first (see faq).

It's always possible that a new cylinder can leak. You can check that by careful monitoring of the level in the CW header tank, but you have to be using no water from it, over a period.

If you can get the whole house quiet, and pressurise to 2.5 bar, everything off, you can sometimes hear a leak with a "listening stick".

 

[jerryl]

So could we be talking of just a pin prick in the system to be enough to cause the pressure to drop so quickly or are we looking for something like a broken joint.

 

[jerryl]

Our plumber has now found a pinhole in the diaphram of the expansion vessel which he believes could be the problem and believes that changing this will rectify the problem. Would a small hole in this allow the pressure to be lost so quickly? Any comments

 

[jerryl]

Our plumber has now found a pinhole in the diaphram of the expansion vessel which he believes could be the problem and believes that changing this will rectify the problem. Would a small hole in this allow the pressure to be lost so quickly? Any comments

Surely someone out there can give me their opinion please

 

[Strachan]

The diaphragm wouldn`t work correctly if it has a hole in it. Ask your plumber if he`s so confident that this is the root of your problem he`ll do a "no fix no fee" on the repair?

 

[jerryl]

The diaphragm wouldn`t work correctly if it has a hole in it. Ask your plumber if he`s so confident that this is the root of your problem he`ll do a "no fix no fee" on the repair?

Whatever the outcome though wouldn't he have to replace this now anyway?

 

[Strachan]

Certainly!

 

[jerryl]

Hi Strachan
When you say the diapharm wouldn't work properly do you mean the system would lose pressure quickly?