Cold water tank size

[Robbox]

We have a 50 gallon cold water tank. We already have one pumped shower and want to install another. All the plumbers so far have made no mention about putting in a second tank, until today. The plumber who came round today, to price the work, said I should have a second tank for two power showers. Our mains pressure is about 1 bar, 10l/m.

 

[JohnD]

What size is your hot-water cylinder, and what colour?

 

[KenGMac]

for background reading a current post

Replacement cold water tank
Discussion in 'Plumbing and Central Heating' started by Grenage, Saturday at 6:15 PM.

 

[Madrab]

If you want the potential to run 2 pumped showers together or even concurrently, you'll need to plan the size of the HW system and cylinder before worrying about how large the Cold Water Cistern (CW Cistern) is. You need lots of hot water to run 2 pumped showers for a decent duration .... pump size dependent and ideally dedicated feeds etc to ensure one doesn't starve the other.

Use the current use with 1 as a model, how long does it take to start to run cooler and what size is the cylinder ...... 2 showers with the same draw will approx half that time. Roughly double the hot water capacity to level that back up.

At 10l/min and 1 bar mains then you'll also need to watch how quickly you empty the CW cistern and whether the supply can top it up fast enough. May need to look at the supply pipe up to the float valve to maximise flow.

Careful bit of planning and design to be done by your plumber methinks to get it all to work together.

 

[Robbox]

@Madrab thanks for the advice. The HWC is ~110cmx45cm and green insulation. Just a five minute shower at 10l/m is 50l, so after two or three concurrent showers the HWC would be finished and cold. The CW tank would be almost half empty. I guess to be safe, we need to replace the HWC and add another CW tank.

 

[Madrab]

Just a five minute shower at 10l/m is 50l, so after two or three concurrent showers the HWC would be finished and cold

Don't think of it like that. While you are using the hot and cold water, it is being replenished by the CW cistern refilling and the cylinder is being refilled & then re-heated by the heat source. There are also other factors to take into consideration.

How large is the supply pipe to the CW cistern, how good is the water flow into it, how quickly the cylinder can recover, pipe layouts, heat source, etc.

I would recommend that you get an experienced plumber to take all the deciding factors into consideration and use his knowledge to design a system that will give you what you need.