Hissing sound coming from heating system

martineire

Was called out to my friends house to have a look at a problem they were having with there heating system. There is a hissing sound coming from the rads down stairs (even with heating off). its an open vented system, gas boiler (myson marathon 1000B). I checked for water in header tank in attic and its full. blead all rads in house, boiler turned off i checked that the CH pump was turning off too. But there still is a hissing sound coming from rads downstairs (like there is water flowing) but CH pump is turning off. I cant understand it, very weard. Next stop drain down heating system. Any ideas?

wilser

Is there a back boiler fitted? if so maybe the pump from this is running?

martineire

No back boiler she has a gas fire. Very strange ill drain the system down tomorrow and ill let ya know the outcome.

Jedstaff

I had a similar problem on a job a few months back. Had to open a concrete floor and found a burst water main. The heating pipes were nearby and the noise just travelled .

Outkast_IRE

Jedstaff wrote: »

I had a similar problem on a job a few months back. Had to open a concrete floor and found a burst water main. The heating pipes were nearby and the noise just travelled .

I second this , had a similar experience myself, turn off the stopcock outside and see does it stop, if theres likely to be other water services running there shut off those valves one at a time and see does it stop