Gas pipe gurgling as if water inside

[lee22]

Got a problem with our hot water boiler upstairs. Its an old Medway system. Radiators are on another boiler downstairs. The medway has a slight water leak and is awaiting a visit from our plumber. We haven't used our heating for a few days but today when I switched it on there was quite alot of gurgling from the gas supply pipe as if there is fluid inside it, something I've never heard before. Is it possible for moisture to build up in the gas supply if its not used, or is it more likely that the water leaking in the Medway upstairs is finding its way into the gas pipe? If this is the case then surely it would be possible for the gas to leak???

[htg engineer]

If you suspect any problems with gas then you need to get it checked. If you suspect water is getting into the gas mains then you need to contact Transco / Northern Gas Networks etc.

It is possible to get water in gas pipes sometimes due to gas mains work in the area or a crack in mains where rain water can get in. It would be very unlikely for water to get into the gas supply via the hot water heater upstairs.