Any plumbers out there?

[RogerS]

Not quite...there is the cold tank in the loft that feeds the hw tank. I grant you, the size isn't exactly huge and there ain't no way of getting a larger tank up there Having said that there are some large tanks up there but not connected and no idea why they've been taken out of service. If I managed to get them all filled up and connected together then that would solve the water availability issue, I think.

 

[sunnybob]

No.
and just for luck, NO.

you dont understand gravity and pressure.
The hot pump will take water out of the hot tank and pressurise it. You cant compress water, so the only way you can pressure it is to force more water through the pipe than would move by gravity. So your hot tank will empty faster than the water will fall under gravity into the hot tank.

Connect two cold tanks, with two seperate LARGE bore pipes into the hot tank, and it might keep up. Three cold tanks with three large bore pipes would most likely do it. But then the water is leaving the tank faster than the heater can keep it hot.

What you are describing is doomed to failure and it will be an expensive and possibly very dangerous failure.

And dont even think about calling your insurance company to repair the damage.
Rip it all out, have a pressurised system installed. The scrap copper and brass will go a fair way towards the new build.

 

[RogerS]

No.
and just for luck, NO.

you dont understand gravity and pressure.

Umm...yes I do

The hot pump will take water out of the hot tank and pressurise it.

No it won't. I don't think that the pressure will change in either direction. If anything it will create low pressure. Atmospheric pressure/gravity will then replace the water extracted by the hot water pump. This water will come from the cold water tank.

It is exactly what we had at our last house. A power shower fed from a large Stuart Turner Monsoon pump. Cold feed 22mm from the cold tank in the loft and hot 22mm feed from the hot water tank into the pump. I could have a good shower followed in quick succession by my wife having hers. We never ran out of hot water. It worked perfectly fine. The hot water tank was also fed with 22mm pipe from the cold water tank.

All vented.

.....[/quote]

 

[sunnybob]

nothing else to say

 

[Phil Pascoe]

I would imagine that as a hot water tank isn't designed to be decompressed you would need a 28mm or 35mm supply if a really powerful pump were to be fitted.

 

[jimmy_s]

Roger

Just seen your pics. It looks like you have a borehole pump feeding the tanks with the tanks connected to a cold water booster pump. The cold water booster is then serving your cold water services and also an open vented hot water cylinder?

You could as you say just fit a shower pump to the hot water cylinder. if you did follow this route then I would go with a negative head type pump so the hot water service is pressurised and fit a PRV to both the hot and cold water services to make sure the pressures at your showers etc are balanced. If you go down this route you could stick with the open vented cylinder.

The other option is to use the cold water booster pump to serve the whole house - hot and cold. You could then do away with the header tank and wouldn't need a shower booster pump but you would need to change your cylinder to an unvented one. Open vented cylinder would not work. You would need to check the duty of the booster pump to make sure the flowrate is ok.

 

[RogerS]

Many thanks, Jimmy. That gives me all the accurate information that I need to move forward.

 

[squib]

What Jimmy said....boost the supply,balanced hot and cold and unvented hot water cylinder is the way to go.

 

[squib]

By the way, Anchor pumps or Pumps UK were both very helpful when I had a similar issue in our new house and in the end I bought a Grundfos home booster pump, slightly different situation though.