shower pump, positive or negative head????

[tamrasi]

Hi, I am planning an en suite with a shower just below the water tank which feeds the hot water container.
When holding the showerhead high it might be higher than the outlet of the tank.
The cold water comes from the mains supply. I have been told that a pump for positive head will do, as long as I put it ar the same level as the hot water cylinder, which is on the floor below the new shower.
Does anyone have any experience with such an installation and can confirm this? Or will I need a pump for negative head anyway?
Thank You Tamrasi

 

[hazetimesfive]

if the outlet is higher than the water level in the tank then you would need a neg pump, or just lower the shower head until the water starts and then you can put it as high as you like

 

[JohnD]

The cold water comes from the mains supply.

you must not pump water from the mains supply.

You need a balanced cold feed from the cold water tank.

 

[tamrasi]

The cold water comes from the mains supply.

you must not pump water from the mains supply.

You need a balanced cold feed from the cold water tank.

Thanks for pointing this out to me, I was planning a pump only for the hot water. I was told a thermostatic mixer could cope with pressure differences.
Thank you

 

[ChrisR]

No you can't mix mains and tank fed, it almost always fails..
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The head thing, is relative to the water in the COLD tank feeding the hot one which will be above it, either a floor above (loft) or sitting on top of the hot directly.
As long as it's high enough for water to flow unaided from the showerhead, you don't need a neg head pump.