What is the impact of removing cold water tanks from the loft?

[nmg196]

I'm considering a loft conversion in my house as as part of adding an extension. However right in the dead centre of the most useful space, are the two tanks for cold water and central heating.

If I have an open vented setup, what is the least I can do to convert to mains pressure and remove the large cold tank at the least? I guess the small tank for the heating could be reclocated so it's not in the way, but I'm guessing the existing cylinder for the hot water is not designed for mains pressure and would have to be replaced? If so, what would replace it? Can I get a mains pressure cylinder and put it where the current cylinder is and can I keep my existing boiler if I keep the smaller tank?

Thanks!

 

[Terrywookfit]

Yes Yes and Yes.

Providing you have sufficient cold water supply

 

[nmg196]

What would the pressure need to be? I have a pressure gauge I bought when there was a temporary loss of pressure many years ago.

 

[endecotp]

You need to measure the flow rate, not the pressure.

 

[footprints]

Easiest solution would be to consider changing to a Combi boiler, no tank in the loft mains pressure to your shower and you gain the space where the cylinder was.

 

[nmg196]

It's a 4 bed house with 3 showers though, so I wasn't sure a combi would be "gutsy" enough for that?

 

[JohnD]

What would the pressure need to be?

it's not the pressure, it's the flow that is likely to be your problem.

edit
too slow!

20 litres per minute will be fine

12 lpm adequate for a shower but meagre to fill a bath.

In an old house you may need to replace the supply pipe and valves, and some of the internal pipes, with larger ones.

this is not as difficult as you think.

 

[footprints]

Yes you are right it would struggle.

 

[Gasguru]

Screw in a pressure gauge nearest the incoming water main.
Measure the pressure with no flow at various times of the day (you might be on a shared main and the pressure could vary).
Ensure the boundary and internal stopcocks are fully open.
Then open a cold tap and record the pressure at different flowrates...say 10 litres/min, 15, 20 etc.
Use a measuring jug and stopwatch...most Weir gauges are junk and inaccurate.
Once done you can tell whether there are any problems and what's the best way forward.

With that size house and bathrooms a combi (including storage type) is not a good idea.

 

[nmg196]

it's not the pressure, it's the flow that is likely to be your problem.
In an old house you may need to replace the supply pipe and valves, and some of the internal pipes, with larger ones

Its from 1996 so not too old. It seems to all be 22mm or 28mm everywhere I can see pipework, except for one run to a single hot tap.

 

[nmg196]

Can a high pressure cylinder fit in an airing cupboard where the old tank was or are they a lot larger?

 

[footprints]

They are a lot taller and the tundish discharge will need to run outside by gravity.

 

[Madrab]

If you have three showers then in this case the pressure is just as important as the flow. You can easily have 20L/min @1.5bar but the minute you go to 2 or even 3 showers that drops to .75bar then it's a waste of time and your dancing about the shower trying to catch the water.

For your application I would advise, if you want to be able to use all three showers at the same time, that you want around 3 bar dynamic pressure with an absolute min of 20L/Min on a 22mm supply to and from the cylinder.

The size of the cylinder will be dictated by the amount of water you will need. For 3 showers then at least a 180L cylinder, you can shop about and compare sizes

 

[nmg196]

Thanks Madrab. There are only two of us in the house at the moment but I don't want to fit something which doesn't eventually scale when our baby arrives in a few months. That said I think the chances of all three people needing to shower at the exact same time is pretty negliable. I would plan for two showers max. I will measure the pressure and flow rates when I get some time.

 

[Gasguru]

Baby girl or boy...better get a whacking great cylinder if it's a girl. Been called back to installs where a teenage daughter has drained the cylinder every shower.