Flood in bathroom & unvented Ariston water heater

Joe1919

My bathroom flooded yesterday. Fortunately I was home when it happened but there is some mess. The culprit initially seems to be the Hepworth half inch 90 degree bend (grey/white) which seems to have lost its grip on the pipe and blown it out. However, I have examined this unit and can see no obvious problem.

I am a bit concerned about the Ariston unvented water heater. The unit has worked well for over 8 years. This unit is under mains pressure (40psi) but also builds up additional pressure due to the expansion of heated water to 90 psi. (there is a combined pressure and non return valve on the cold inlet.) Perhaps this valve is sticky and allowing the pressure to go above this. I am also thinking that perhaps this pressure is to high for these plastic fittings.

Any thoughts?

Your right to be concerned it's a very badly fitted water heater.

Rip it out and have it fitted by a plumber who understands unvented water heater requirements, those heaters can hit 82c+ And as your is fitted without taking expansion in to account it is more likely to burst which can then be made more dramatic if someone gets scolded.

As the your installation is the cause of your water leak woes you need to start again, replace the plastic with copper, fit a 3 1/2 bar pressure reducing valve if the incoming mains standing pressure is over 3 1/2 bar, you need to fit a expansion vessel as close as is practical to the heater on the cold side(never on the hot also Ariston call their expansion vessel Kit A), the Chrome safety valve should be fitted on a T piece leaving the cold side open for expansion, personally I would fit a 6 bar safety valve as you can then connect a 1/2inch pipe to direct the water to a safe place if ever it opens, reducing any potential flood damage, I would also fit a blending valve to prevent scalding water from reaching the taps.

Have a look at the UK fitting instructions which format the installation requirements for these heaters.