Water pressure pump

[geordysurfer]

Many thanks buildersmate for your answer. Yes please I would like more advice. I have recently installed a water pressure fed Valiant heater, replacing an electric one which worked well but only stored 50 ltrs!!! In a morning the heater will show the exit water temp as 50 degrees (more or less) but this falls to 30 degrees by lunchtime. After about 5pm the temp goes back up to 50 degrees plus. The system is fed by gas bottles which are stored outside. As I said, I am unable to install a water header tank to control the pressure, which, although not wild, is more than adequate. I assumed that the water pressure was the issue, the only other options, obviously, are the heater and the gas. Any advice would be greatly appreciated as this is frustrating to say the least.

[buildersmate]

I'm struggling a bit to know what this gadget is - you say it stores water, not heats it only as hot water is needed. You also seem to say it stores water in the boiler - not connected to a separate hot water cylinder.
If the above assumptions are correct, how do you know that the lower temperature (that falls during the morning) is not the direct result of usage of the hot water that has been gradually heating up overnight, but which is taking time to reheat, as cold water feeds into the store?
I am convinced that pressure is a red herring. In most domestic systems, the mains pressure is at its LOWEST in the morning (when the whole neighbourhood awakes and wants a shower) and the supply pipes struggle most to cope with the demand. But if this gadget is STORING hot water inside it, not instantaneously heating it on demand, pressure is not a factor.
Gasman may have a better analysis of this situation.

[gasman]

Forgive me for gatecrashing a question directed to buildersmate. I am assuming from you're description, that this is not a standard wall mounted Combi or system boiler. Am i correct ???
Or do you have a Unvented free standing LPG core fired water storage heater ??? ( A large 5-6ft cylindrcal vessle with a draft diverter and a flue out of the top of it with a ring burner in the bottom ) But then again I have never seen one made by Vailant. (confused)!!!
I totally agree with 'BM' on that the pressure is irrelevent Because pressure has different affects on a combi as in low pressure would increase the water temp. So opposite to what you are experiencing.
Can you shed some light on to the type off installation you have and the model installed. As each one would have a different answer / soloution.

[buildersmate]

Agree, GM. And I think he must have an unvented LPG water heater - something I'm not familiar with.