Ariston water heater

25 Mar 2004
Reaction score
United Kingdom
Just had a 15l Ariston water heater fitted and it is constantly dripping through the Tundish.

On the pipework from the mains is a Pressure reducing valve, Then they have put the pressure relief valve to a tundish, then the expansion vessel, then into heater.
Have they done the pipework correctly?
Should the expansion vessel go before the pressure relief valve?
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Usually on an unvented heater there would be:

incoming supply > isolator > cold draw off to other appliances > check-valve > expansion vessel > Pressure relief valve (6 bar) > water heater

If the mains is high pressure (>3 bar) then a Pressure Reducing Valve is fitted after the isolator

incoming supply > isolator > PRV (3 bar) > cold draw off to other apps > check-valve > expansion vessel > Safety Pressure valve (6 bar) > water heater
In reality the expansion vessel in the position yours has been fitted still shouldn't be making the Temp/Pressure relief valve open. Might be worth checking that the exp. vessel has the correct pre-charge and/or the Pressure Reducing Valve has been set correctly
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Looks neat enough and EV is correct type.
As @NotSoNewboy said check the setting on the reducing valve and the air pressure on the EV should be 3.5bar to atmosphere.

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