Water flow rate and unvented cylinder question

[wwwebber]

Hi - just realised I need a bigger hot water tank and bigger cold water tank to service our new mixer shower. This has now pushed us into the the realms of fitting a unvented cylinder instead.

However, the mains water feed into our house is only 15mm with a flow rate of approx 12lm out of the kitchen tap and a static pressure of 3 bar.

Is this good enough to run an unvented cylinder and still get a decent flow out of the mixer shower ?

Cheers.

 

[oldbuffer]

No, the flow rate is too low. Say your shower is 10 lpm (and some can run to 30 lpm), then if its running, there's only 2 lpm for anything else and its not enough.

However, if you really have 3 bar pressure, the low flow rate may be caused by obstructions / restrictions. Test what the pressure is at an "open pipe" outlet, with one other outlet (kitchen tap) running. If its over 2 bar you might be in with a chance after some pipework changes. If your kitchen tap has an isolation valve on it, unless it's a full bore one, it will restrict the flow rate to what 3 bar can push through a 10mm diameter.

 

[wwwebber]

ok, ran the kitchen tap and re-tested the water pressure at a nearby outlet - it came in at 1 bar

Am I stuck with a vented system ?

 

[Dan Robinson]

Not necessarily :

 

[wwwebber]

Thanks for the replies.

I'm pretty much resigned to enlarging our hot & cold water tanks and then pumping them to our mixer with a twin pump. Looking at approx 200 litres for each tank which should suffice.

Cheers.

 

[muggles]

So why not have a pressure vessel as Dan has suggested? That'll give you 3 bar hot water at a much higher flow rate than your incoming main

 

[wwwebber]

Because my thermistatic mixer needs equal hot and cold pressure

 

[muggles]

Which you can get with the pressure vessel setup...

 

[wwwebber]

That'll give you 3 bar hot water at a much higher flow rate than your incoming main

Doesnt sound equal ?. And can it be heated indirectly ? And does it need a cold water tank ?

 

[Dan Robinson]

Is if the cold is done too?

Yes

No.

 

[muggles]

Is if the cold is done too?

Yes

No.

What Dan said

 

[wwwebber]

So two pressure vessels ?

 

[Dan Robinson]

eh?

 

[wwwebber]

eh?

You said if the cold is done too ?. Done how ?

 

[Dan Robinson]

A balanced supply.

If you have a cold water storage tank then removing that in favour of accumulator(s) will by definition result in a balanced supply as that is where you cold is fed from as well as the hot.