Advise on Attic Water Tank Size Needed

Bluscreendream

Hi guys,

I'm working on a build at the moment and we're coming to the planning of the bathroom, I'll be putting in a normal freestanding bath (175cmx75cm, 224 litres) and I just wanted to ask a fairly dumb question :rolleyes: and get opinions on what capacity attic water tank and hot water cyclinder I should get. There will also be a separate shower unit and a sink and also a sink and washing machine in the kitchen. Nothing fancy.

many thanks.

delfagio

Hi there,

I am building a new 4 bed house that's 2500sq ft. Now our house has a main bathroom with bath toilet shower and sink. There's 2 ensuites upstairs and a toilet downstairs which all have a sink toilet and shower.

We installed two 50 gallon cold storage water tanks in the attic, so that's approximately 450lt storage of water. We have a 300ltr hot water cylinder.

We have two storage tanks in the attic mainly due to the amount of bathrooms and the fact that we have a pressurized water system which is at 3bar pressure. One of the downsides of pressurized systems is that you can use more water when showering, running taps etc.

Bluscreendream

Hi delfagio,

Thanks for the reply. Is there any rule you used to calculate the tank capacities you needed?

littlemissfraze

From the plumbers guide size tank as per these guidelines:

Cold water storage:
1 bedroom - 210litres per Bedroom
2 bedroom - 130litres per Bedroom
3+ bedrooms - 100litres per Bedroom

BryanF

littlemissfraze wrote: »

From the plumbers guide size tank as per these guidelines:

Cold water storage:
1 bedroom - 210litres per Bedroom
2 bedroom - 130litres per Bedroom
3+ bedrooms - 100litres per Bedroom

Is this a building regulation requirement ? Thanks

Gumbo

BryanF wrote: »

Is this a building regulation requirement ? Thanks

Technical Guidance Document Part G.
Section 1.6.

Minimum storage of 212 litres for a 3 bed and 340 liters for a 4 bed.
Those are the minimum requirements but I assume the plumbers guide above aims to over comply with these.

Metric Tensor

Remember if your water supply gets shut down (i.e. pump goes out, public supply is off) the tank in the attic is all the water you will have to survive for flushing toilets, etc.

This needs to be balanced against the dangers caused by stagnant water if the usage is not high - of course you're not meant to drink this water but sometimes kids do.

The TGD G recommendation is a minimum as kceire pointed out. I'd always go higher than this.

delfagio

Bluscreendream wrote:

Thanks for the reply. Is there any rule you used to calculate the tank capacities you needed?

Hi Bluescreendream,

I didn't use any calculation, this was what my plumbers told me I need. They insisted I get them two tanks to be installed. They said as I had a 4 bed house I was going to need 2 x 50gallon tanks in order to have enough water storage and also because I was having a pressurized water system which typically causes you to use more water than a gravity feed system.

Which makes sense when you think about it. If your water was turned off for any reason, you would want to ensure you have enough water storage for toilets, showers, washing etc.

Bluscreendream

Thanks all for the advice so far and sorry for the late reply, I'm still not sure on what capacity would be required for an attic water tank and hot water cyclinder, here's what they would need to serve;

1 toilet
1 shower
1 bathtub (224 litres)
1 hand sink
1 kitchen sink
1 washing machine

any ideas....

Thanks,
Blu

Metric Tensor

The number of people or potential people being served is more important.

How many bedrooms in your house OP?

Bluscreendream

Metric Tensor wrote: »

The number of people or potential people being served is more important.

How many bedrooms in your house OP?

Hi Metric, it's a bungalow, one bedroom/living room/bathroom & Kithchen. It's just me and my girlfriend, no plans for kids

delfagio

Bluscreendream wrote:

Hi Metric, it's a bungalow, one bedroom/living room/bathroom & Kithchen. It's just me and my girlfriend, no plans for kids

I'd still plan for more people. If it was me I would install 2Nr tanks in attic. Cost to install extra tank would be little.

BarneyMc

delfagio wrote: »

Hi Bluescreendream,

I didn't use any calculation, this was what my plumbers told me I need. They insisted I get them two tanks to be installed. They said as I had a 4 bed house I was going to need 2 x 50gallon tanks in order to have enough water storage and also because I was having a pressurized water system which typically causes you to use more water than a gravity feed system.

Which makes sense when you think about it. If your water was turned off for any reason, you would want to ensure you have enough water storage for toilets, showers, washing etc.

This is very much what I was advised also for similar needs.

Calahonda52

kceire wrote: »

Technical Guidance Document Part G.
Section 1.6.

Minimum storage of 212 litres for a 3 bed and 340 liters for a 4 bed.
Those are the minimum requirements but I assume the plumbers guide above aims to over comply with these.

Based on the OP's reply to this, it seems the OP has no interest in complying with the Building Regs for water storage so one wonders what other shortcuts have been/will be taken that will make house non compliant with regs and potentially unsaleable.
Regs are for others perhaps

Gumbo

Calahonda52 wrote: »

Based on the OP's reply to this, it seems the OP has no interest in complying with the Building Regs for water storage so one wonders what other shortcuts have been/will be taken that will make house non compliant with regs and potentially unsaleable.
Regs are for others perhaps

One of the reasons why I haven't replied since tbh.

Metric Tensor

For your size house OP:

TGD G: Minimum 212l - (installing this size proves compliance with the building regulations on the matter)

BS 6700: At least 230l

CIBSE Guide: 220-300l (If I recall correctly)

Various other guidance: 24 hours storage - taking EPA COP of 150 l/person/day x 2 would give 300 litres. Although as occupant numbers increase I would argue that 150 x occupant number would begin to overestimate 24 hours usage.

NB. If you have a pressurised system you will use more than a gravity system. There is no explicit reference to this in any of the guidance I have read.

atech

Calahonda52 wrote: »

Based on the OP's reply to this, it seems the OP has no interest in complying with the Building Regs for water storage so one wonders what other shortcuts have been/will be taken that will make house non compliant with regs and potentially unsaleable.
Regs are for others perhaps

What has led you to believe this?
From my reading of it the OP has suggested they think they need a water tank and hot water cylinder capable of at least filling a 224ltr bath among other things so if anything they are unsure of how much above the min 210 ltr for a one bed they should go to allow for all of these.

Metrics advise is sound; if the house is likely to only cater for 2 occupants for the future then 300 ltrs for a cavity fed system should suffice for 24hr storage.

While I'm not a plumber and don't know what the heating system is I won't pretend to know what the general guidance on sizing hot water cylinders are but if 300ltrs is sufficient for cold water then off the top of my head I'd guess a 180ltr cylinder should be sufficient to to meet the daily hot water demand.

Obviously he should ask his plumber to check these sizes are sufficient first before ordering anything but as he was only asking for opinions I take it he is just trying to gauge costs/options at present and not trying to ignore regulations.

SpudBr

I would like to buy a tank of the following dimensions - 3.2 X 3.7 X 1.10 deep . I would be a PVC tank . The reason I want one that size is because I have this pond in my back garden which is sealed with a butyl sheet but I have replaced this on two ocassions already because of leaks . I dont want to go to the expense yet again of getting another sheet , it will be expensive and it will only last a few years . So I hope a tank will solve the problem . I want it to be as near as possible to the size of the existing excavation in the ground . Thanks .