UK Plumber Forum

[Larryhud]

I have an Valiant EcoTec 838 boiler (Combi). The gas pressure at the boiler is being measured at 14 mb (ish). The main gas regulator is showing a pressure of 20mb. In order to cure the problem, I was advised to change the pipework from 14mm old Iron pipe to 28mm and 22mm copper pipe. £1000 job.
For information the length of pipe is about 13m and has 7 elbow joints. It has 28mm for roughly 2/3 of the length and 22mm of the other 1/3.
When the job was completed the pressure remained low > 15.5mb at the boiler. I was advised to call out Valiant to have the boiler checked as still under warranty. The engineer came out and said the boiler was fine – he even changed the gas valve and air/fuel mixture sensor to be sure. He was adamant that the main gas regulator and the boiler was fine and it MUST be the pipework. The Valiant engineer said the pressure was perfectly acceptable for the boiler and there was no issue to solve – he didn’t seem to be concerned about the pressure drop.
I contacted the plumber who came back to say the pipework is new and was specced correctly > the issue must be elsewhere.
I have spoken to several plumbers who have shown little interest in this issue. They either say it is fine, why bother? Others say there shouldn’t be a drop but don’t know the cause. Others say it must be the size of the pipework. But none have offered a way forward.
I suggested putting nipples at various points the pipework to test and eliminate various sections of the pipe. Then I thought why AM I suggesting ways to investigate?! I have no expertise!!
So I am posting here for expert opinions as at this point I am lost

[REDSAW]

How long ago was the boiler fitted?
Do you live in a rural area?
whats the pressure at the meter with appliances running and not running?
are any pipes below ground?

[Larryhud]

How long ago was the boiler fitted?
> 8 years ago, still under warranty - serviced every year
Do you live in a rural area?
> No, a suburban area
whats the pressure at the meter with appliances running and not running?
> 15.5mb with the boiler running (during testing?)
are any pipes below ground?
> No

[REDSAW]

change the iron pipe for 15mm copper. sounds like the pipe is de-scaling and clogging up the gas valve at boiler. then get the valve adjusted to achieve around 16-17mb allowing permissable drop through meter and pipe run. it might not be posible to clear the gas valve so a new one may be required.

[joni os]

The new pipework is sized correctly. This does not exclude the possibility of obstruction in new pipes. Could be flux, solder, water or just debris that dropped in when pipework open.
Gas fitter could open pipework at boiler and meter and flush with water then air to remove the water.
If it is the same man who installed pipework and he is confident excessive flux is not the problem, putting a vac. on the largest open end of pipework may be all that is necessary.

[REDSAW]

The more i think and re-collect i think the iron pipe scalling and clogging up valve is highly likely seeing as it has been changed before!