Unvented Cylinder Discharging Water
Water running from the tundish under the cylinder, either continuously or after each heating cycle..
Water running from the tundish under the cylinder, either continuously or after each heating cycle.
What is actually going on
Water running from the tundish under the cylinder, either continuously or after each heating cycle.
The realistic causes, in order
An expansion vessel or internal air bubble that has lost its cushion, so expansion has nowhere to go A passing expansion relief valve held open by debris A failed temperature and pressure relief valve, which is the safety device of last resort
What we test on site
Which valve is actually discharging, identified at the tundish Incoming mains pressure and the pressure reducing valve setting Vessel charge, or air-gap re-charge on a bubble-top cylinder
Get an unvented cylinder discharging diagnosed properly
Re-charging the vessel and replacing the passing valve resolves the majority of cases.
Questions we get asked
Does an unvented cylinder discharging mean the cylinder needs replacing?
An expansion vessel or internal air bubble that has lost its cushion, so expansion has nowhere to go
What normally puts an unvented cylinder discharging right?
Re-charging the vessel and replacing the passing valve resolves the majority of cases.
Is it safe to keep using the system with an unvented cylinder discharging?
A discharging temperature and pressure relief valve is a safety warning, not a nuisance. It should be investigated promptly by someone qualified in unvented hot water systems.