Drop in gas pressure between inlet and boiler

[dk3]

hi, had my boiler serviced and engineer has diagnosed a drop in pressure of gas between inlet and boiler since he last serviced it. boiler is in full working order. he tested presure of gas coming in to house which is fine. he suspects either blockage in the pipe or damage to the pipe(which he said is unlikley) the pipe is from understairs to outside the house(under floor and driveway) up wall and in to back of boiler, he said options are to have a new pipe between under stairs and boiler(routed internally) or to dig up and look at existing pipe. does this solution sound right? can a pipe be unblocked or checked in a similar way to drains? how would a pipe get blocked as it is never open either end? boiler works fine, he said there is no danger but boiler will not function to its best and this will be more noticeable trying to heat water in the winter which I can verify. sorry for long post!!

 

[gremlin16]

Did he check for black dust in pipe work?

 

[dk3]

Hi Gremlin. I dont know, just googled it there, I can check with him but he didn't mention it when I quizzed him on how there could be a blockage in a concealed pipe.

 

[namsag]

As gremlin says.
Good chance black dust in gas valve filter or settled at the bottom of a pipe drop in an elbow.
It can be blown out as with usually no need to change pipework

 

[Youllneverguess]

I go with namsag on this one.

 

[dk3]

cheers, he did clean the gas valve filter and there was a bit of crap in there but that didnt resolve it, so he began looking at pipework. he had me blow through the pipe (meter was taken off) and although air came through he still suspected a blockage.

 

[Youllneverguess]

What was the pressure at each end (dynamic), and was the gas rate?

 

[simond]

I assume he did a 'tightness test'? If you have a buried section of pipework another reason for pressure drop could be a leak.

Of course, the other reason could be he didn't measure it properly last time and the pipework was (and is) undersized. Very common if it's a combi.

 

[dk3]

thanks for replies, I'm not at home so cant check the pressures, will do tomorrow though. if pipework is undersized and needs replacing I think the internal re-route is prob best action. sound like from suggestions I should get him back in to double check readings and try to clear pipe before doing any works.

 

[Youllneverguess]

An air compressor maybe, but there are hse guidelines for working with compressed air.

 

[dk3]

cheers youllneverguess, sorry meant him to check readings and check pipe, I wont be touching it.

 

[Agile]

Its unlikely but a small leak in an underground pipe can let in water which can restrict pipe flow.

Mostly a problem for Transco with street mains.

For a domestic pipe a compressor at about 30 psi will usually blow water out. Transco use a nitrogen cylinder so that they dont end up with an explosive mixture in their pipework.

Tony

 

[Youllneverguess]

I think SimonD put it nicely - the problem was there from the beginning, but perhaps he is short of work at the moment...

 

[dk3]

not sure about that youllneverguess, he has done the servicing for years and at previous properties and my mates too. Agile, there is a buried section, I asked about a leak/danger, he said he would cut me off there and then if he suspected a leak. I dont have the readings but i could get them from him. thanks for all replies, think I will need to get someone out for 2nd opinion?