Underfloor heating manifold hissing noise

22 Jan 2012
Reaction score
United Kingdom
Hi, I have part underfloor heating & part radiator system.
The boiler is losing pressure, so I feel there is a leak somewhere.
I've noticed the underfloor heating manifold hisses around the flow gauges when the heating is turned off (when cooling)
Is it normal to hear hissing at manifold or could the pressure drop be coming through air leaking. No leaking water is visible at all.
Sponsored Links

It is likely that you have a leak on one of the UFH ccts, if the leak is not visible it is likely to be underfloor

Start by thinking if any work has been done in the UFH area that may have involved drilling into the floor or nailing of floorboards etc? ;)
Can you eloborate?
Boiler has only just started dropping. No joins in underfloor circuits so I'm struggling to accept that it's leaking from one of the circuits.
Why would there be a hissing noise at manifold from a leak somewhere underfloor ?
I thought leak would more likely be on radiator circuits or air in underfloor heating system

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local

Sponsored Links