Water tank size

[marief]

I'm doing up my first house which is a large victorian terrace and need to install a new water tank in the loft. It only supplies the hot water system (cold is from the mains). Can anybody tell me how I calculate the size I'd need as the old one is basically an old baby's bath :blush2:

The house is 5 floors, currently 2 bathrooms (bath, shower, basin, toliet), 1 wc (sink and toilet). Then there is the kitchen and a laundry room which has 2 sinks.

I'm planning on moving it into the loft space so I'd need it to be a coffin tank as the opening to the loft is tiny. I'm looking at the 25gallon one, do you reckon this will be sufficient?

Hope you can help!

 

[Last Plumber]

I know I'm jumping gun here because you have not yet decided on volume but a word to the wise, water weighs 10lb ( roughly ) per gallon. Make sure it's properly supported.

 

[PlumbBobBob]

you should really go for a 50 gallon cwst if you can get it in. are you doing the work yourself or getting a plumber in? there are certain regulations that need to be followed.

 

[Destroyer2813]

Any shower pumps?

 

[marief]

Wow, thanks for the quick replies.

It'll be well supported as I'm making an atomic bomb proof structure for it to live on.

I don't plan on having any power showers so shouldn't need a pump as the house has excellent water pressure.

I was planning on doing the job myself as I've done quite a few other plumbing jobs before building up to this one, which regulations are you referring to?

 

[Destroyer2813]

Even without pumps I recommend 50 gallons, by law 30 the kit will come with the tank use all the bits not throw them away or leave in a bag in the loft like I've previously seen. If possible position the tank over a supporting wall

 

[ShaunCorbs]

anyone else thinking unvented cylinder would be perfect ?

 

[Last Plumber]

What's mains flow rate and pressure like ?

 

[Best]

anyone else thinking unvented cylinder would be perfect ?

Yes, - so obvious if the OP is correct about the pressure and if a plumber could confirm the flow rates then should be the cheapest and best way by far to fit an unvented cylinder. Buying a new cold water tank and kit, plus all new pipework, pipe insulation, valves, overflow pipe, etc, alone would cost a fair bit.
Needs a G3 plumber but and not DIY.
If the OP does still go with a traditional gravity hot water system, I would go with reasonably large cwt capacity - 50 gallon min. You need storage for when mains water if off, that's why they are called cold water storage tanks.