water in gas main

[woolyducks]

Hi All i came home yesterday to start cooking and i could not get any gas at cooker, transco was called and when the guy came he changed the meter and the old one was full of water and water was dripping from the pipe in my property. He says the water must be coming from the boiler and not from the street and then capped my meter. While waiting for a gas man to fix the problem could i ask any of the experts out there, how can water get from the boiler into the gas line what would the likely cause be? i have a revenheat 820 and has worked ok for the last 8 years.

thanks for any help

 

[kevplumb]

new one on me the water and gas sides of the boiler are seperate

 

[croydoncorgi]

Yes - water can certainly get into gas mains. Several years ago, I saw the largest-ever assembly of Transco vans as a result! In that case, a hole in the bottom of a water main had made a jet of high-pressure water which eventually bored through a cast-iron gas pipe and then filled it with water. It took several days to fix it and restart the 100 or so properties affected.

In your example, it's POSSIBLE (if very unlikely) that the boiler dunnit. Are any neighbours affected? Is your meter near floor level / in a cellar AND below the boiler level? Gas pressure would be too low to push water uphill so if your meter is near-to and below the boiler, the boiler is still prime suspect.

If your meter is capped and the gas cut off, there's nothing to be lost from loosening the joint of the gas connection under the boiler. If there's any water there, even just a drip, then the boiler is probably to blame, although it's hard to imagine how water could flow back through the gas valve. Also, if your meter has been disconnected, is there water still coming out of the pipe on 'your' side of the meter?

Has your heating system been losing pressure? Is the indicated pressure 1 Bar? or much higher? For the boiler to cause the problem, there would need to be a hole in the heat exchanger with water dripping into the burner, and from there into the gas valve. The more I think about it, the less likely it becomes!

And the obvious question: had any plumbing work done recently involving changes to pipework? And was it a cowboy doing it?

 

[woolyducks]

Thanks for the advice i got transco back out today as i thought the gas and water would be separate he changed the regulator but no joy, he seems to think that there might be a situation similar to what croydoncorgi says but within my property the pipework runs from the meter and runs in concrete floors and comes up to feed the cooker and then the boiler. The boiler is higher than the meter. My pipe work connects to the meter in about 12 inches of lead pipe which connects onto copper pipe then goes under the floor he took off the bit of lead and water was visible within the pipe but not rising he suggested i turn off the water supply and open the hot and cold taps to drain the water in the pipes and see if the water in the gas pipe rises but the stop cock has seized and i cant turn it off. The pressure on the boiler does fall and i have to keep topping it up.

None of the neighbours seem to be affected

Cheers

 

[kevplumb]

put a cup under the gas pipe and see if you can collect any water cant see how its getting past the gas valve tho you could try turning off the boiler gas tap and see if your presssure drops i assume the tofo carried out a tightness test

 

[kevplumb]

if the copper is run in concrete and not wrapped its possible the concrete has eaten it if the heating pipes are in the same spot could be you have two small leaks water pressure higher than gas pressure hence
not a diagnosis just a thought

 

[woolyducks]

no water dripping from my side of the pipework it is just lying there level with the pipe the heating pipes are no were near the gas run in the concrete cant get a heating engineer out till tuesday if i isolate all the pipe connections under the boiler would that reveal anything

 

[kevplumb]

if theres no water dripping from your side of the pipe i assume the boiler is still under pressure it aint come from the boiler

 

[kevplumb]

close the gas tap on the boiler

 

[croydoncorgi]

From your description, water getting into the gas pipe under the concrete sounds more likely than getting in via the boiler. If you can see water sitting in the pipe but not actually running out of the end, has anything done so far affect the level of the water?

 

[woolyducks]

the water has been turned off at the stop cock and the water in the pipe has dropped but there is still water in the pipe

 

[kevplumb]

close the gas tap at the boiler
turn the water back on and put a bowl under the pipe if you catch water it aint the boiler its the pipework

 

[DP]

What make the boiler?

 

[croydoncorgi]

If the water level in the pipe dropped when the water was turned off and with the boiler switched off throughout, it's most unlikely the boiler is anything to do with the problem.
You will need to pressure test the cold water supply pipe and the gas pipe under the concrete floor. My guess is that both are holed.

 

[woolyducks]

Thanks for all the advice had a guy out today he tested gas side and had a drop of pressure, he concurs with croydoncorgi and i have a leak in the gas supply and the water main, what are the chances of that pray tell
?? he is going to run a new gas supply in the first instance and has suggested getting someone with a mole type machine to run a new water service in.

Thanks again for all the input

wool