Pressure relief on water heater

[Garfield]

I have a freind that is living in a 91 coachman and has a permanent water supply into the van that they turn on to fill the onboard tank. The pump has now died and a replacement is £80, I have a pressure reducing valve that will reduce mains pressure down to whatever you set it to (this is a pressure regulator NOT a flow restrictor). bypassing the tank and pump and connecting the caravan system direct to the mains via this valve is the cheapest and simplest way to sort the problem but I am concerned that if the regulator valve fails and gives the caravan system full pressure, does the water heater usually have a relieif valve? or does something blow?

Thanks

Gary

 

[ProfJohnL]

Hello Garfield

I am glad that you appreciate the difference between a pressure regulator and a flow restrictor. The regulator should be set to 1.2Bar (1.5max at lock off). The water heater (and I assume it is a Carver Cascade in a 91 van) does have a pressure relief valve, however its designed to bleed off excess pressure generated by the expansions of hot water, so its flow capacity is not great, and it would not cope with the full flow of a mains water supply.

However the arrangement you are suggesting is already used in the mains water supply systems like the Carver Waterline and other equivalent systems.

One of the down sides of these seems to be that the flow rate of the water is often less than the flow from a 12V pump

 

[Damian]

Gary, you are right to have misgivings about any system which relies on a pressure reducer to maintain low pressure in a caravan.

If the reducer fails, then mains water pressure will be put into all the pipework, and will blow just about every joint apart.