water heater

[hammers4spanner]

had a call out tonight regarding a leak under kitchen sink , get there nose in and can see the plastic speed fit on the hot has melted and obviously flooded the kitchen .Boiling water coming out the hot taps steaming like hell on earth and pipe insulation melted on the hot pipe underneath instantaneous water heater.
Am i assuming the water pressure is wrong going through appliance causing overheating of water??

guess this proves any doubts about plastic

 

[Reg Man]

Thermostat knackered? Don't you just love plastic?

 

[hammers4spanner]

Its a britony multipoint was thinking diaphram ? not sure if a split /worn diaphram would cause it to overheat

 

[mountainman]

Split or worn diaphragm would either stop the main burner firing or it would only light at low level.
Check that the gas valve isnt letting by leaving a bead of flame on the burner when the taps are off.

 

[hammers4spanner]

Theirs no flame on burner when taps are off its when I turned tap on water just got hotter and hotter till it was scolding hence plastic melting as well as insulation

 

[Reg Man]

Options here. Thermoelectric valve, scaled heat exchanger, excessive gas rate, or low water flow rate.