loft cold water tank (Ed.)

[Graham J W]

Hi all,

I have a very small cold water tank ( 118ltrs) in the loft of my four bedroom house. As there is only two of us we only recently found this out when the shower pump stopped whilst visiting family was using the shower. The loft is very shallow due to the dormer design of the house. The tank is a Polytank 27" x 20" x 20" . Loft hatch is also small.
I think my best option is to buddy up the tank with another one but most, off the shelf, expansion tanks are only about 18 lts. Still not enough in my view.
Questions :

What total lts of cold water storage do you need for a four bedroom house.
How do you connect the tanks together. Ie what size pipes etc.
Do you need feeds and overflows to both tanks.

Many thanks.

 

[Iddy]

Have you got decent flow and pressure to your house? If so, I would consider an unvented (mains pressure) hot water cylinder instead, and do away with the storage tank and shower pump.

 

[cross thread]

You can double up on tanks, cold inlet fitted to one and the outlet fro the other Sotheby’s water is constantly changing when used, one overflow is sufficient.

 

[Madrab]

Normal storage, if you have an open vent HW cylinder would be ~ 50Gal - 227L, double what you have just now. You could set up tandem cisterns, yes.

The size of storage will always be dictated by access. In these circumstances then coffin cisterns are usually used but even then your hatch size probably wouldn't even allow that. You may need to get the hatch size increased.

If your cold water main is good - dynamic pressure and flow (20L/Min @ >2.5bar) - then you could consider an unvented system

 

[JohnD]

It is not an expansion tank, it is a cold water cistern.

Expansion tanks are designed for something else, and are very small, which is why you didn't find a big one.

A full bath holds about 100 litres, so your tank is big enough for the use it is designed for, but clearly your shower pump sucks it dry faster than it can refill. You could fit another tank, but if you have guests who like long powerful showers, they will be able to drain it.

I imagine all the hot water also got used up.

 

[Graham J W]

Have you got decent flow and pressure to your house? If so, I would consider an unvented (mains pressure) hot water cylinder instead, and do away with the storage tank and shower pump.

Thanks Iddy, mains water pressure is quite poor unfortunately.

 

[Graham J W]

You can double up on tanks, cold inlet fitted to one and the outlet fro the other Sotheby’s water is constantly changing when used, one overflow is sufficient.

Many thanks cross thread.

 

[Graham J W]

Normal storage, if you have an open vent HW cylinder would be ~ 50Gal - 227L, double what you have just now. You could set up tandem cisterns, yes.

The size of storage will always be dictated by access. In these circumstances then coffin cisterns are usually used but even then your hatch size probably wouldn't even allow that. You may need to get the hatch size increased.

If your cold water main is good - dynamic pressure and flow (20L/Min @ >2.5bar) - then you could consider an unvented system

Thanks Madrab, poor mains incoming water pressure unfortunately. New hot water , vented, cylinder installed last year with heating system upgrade. It seems just the cold is running out when in higher demand. I think doubling up as cross thread said is my best option.

 

[Madrab]

If you have no other option then cisterns in tandem will be the way to go - The trouble you are probably seeing is that the cistern, as it's feeding both hot and cold, can't fill up fast enough due to the poor water pressure when pumped.