Reduced pressure after Cadent works

[Pipcart]

Something has changed in the gas supply to the boiler in a house we let and it has failed this year’s safety inspection. Last year the operating pressure to the boiler was 20mb and this has fallen to 18.87mb (<1% below 19mb required). 

Cadent resleeved our supply last autumn and are currently carrying out further works to the mains. The loss of pressure to our boiler is probably a combination of

1. Cadnet reducing supply pressure due to works, according to their own helpline.
2. Reduced supply pressure due to sleeving narrowing the supply pipe. Following the test failure they came and opened the regulator to a maximum flow and the last test showed a working delivery pressure of 21.11mb from the meter.
3. Resleeving dislodging debris into the our pipe between the meter and the boiler. There is now a pressure drop of 2.24mb in 22mm pipe which is equivalent to a 182m run, rather than the actual 15m.

 

As responsible landlords we must resolve the situation promptly.

 

The inspection company say that lots of people are having the same problem due to Cadent’s work. They have advised that we replace the 22mm pipe with a 28mm pipe. We have given the go-ahead for this, since it is the only factor in our control, even though it is likely that Cadent created the issue. Cost £1,174.82

 

Cadent’s response depends on the call handler you speak to. One of them wanted to cut the gas off, while others have been very relaxed and sympathetic. Our concerns have been escalated to another department, but we are cautious about pursuing this at the moment, in case the gas is cut off before we make improvements..

 

Does my account of the causes and solutions seem credible? Has anyone else had a similar situation? Do you think we have a case against Cadent?

 

All thoughts gratefully received. - many thanks in advance.
 

[SimonD]

First, I think you need to go back to your Gas Safe Registered person and question why they've failed it because of this reading. Whilst the regs state a theoretically acceptable limit of a design pressure loss of 1mbar this can not be guarenteed in practice so in and of itself it is not sufficient grounds to fail a safety inspection on existing pipework. The important figure is the minimum required inlet pressure specificied by the boiler manufacturer, which is given within the MIs. With 18.87, you are nowhere near the minimum which with some boilers can be as little as 13mbar and with others around the 16.5 mbar mark.

 

The only times a boiler is deemed to be unsafe is if the gas pressure has been proved  to affect the safe operation of the appliance. Refer your Gas Safe person to IGEM-G-11 which they should know and have available on site.

 

And finally, with such a specific measurement, the person has used a digital guage. They're know to be very sensitive,going up and down and under test conditions a varation of 0.25mbar is consider to be no perceptable movement so your measurements are so close to 19mbar anyway, they're not an issue at all.

 

With the information you've given me, you don't need to incur any costs at all for pipework! Get a new Gas Safe registerered person who knows what they're doing.

 

And yes, I'm Gas Safe Registered.

[Pipcart]

Thanks Simon, that extremely helpful. I'll follow that up.