Insufficient hot water for new bath

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Insufficient hot water for new bath

Postby Graeme » Fri Sep 21, 2007 8:46 pm

I've just fitted a walk-in bath for my elderly mum. Unfortunately we don't seem to have nearly enough hot water to fill it (These things hold about 230 litres and need to be fairly full because the occupant sits on a moulded in seat) Our HW cylinder is obviously too small but the cold water tank that feeds it is also too small because first the HW turns cold then it stops altogether! Mains water pressure is relatively low (about 3 bar tops)

I'm tossing up between fitting a massive cold water tank and huge cylinder or just a big unvented cylinder. Space is a problem so last option would be preferable - BUT - would a large unvented cylinder be any good, bearing in mind the low mains pressure? It would also have to be far from the bath with lots of bends + a thermostatic mixer (anti scald because you have to be in the bath before filling!)- so pressure drop might make the flow speed so slow it would take about half an hour to fill the bath!

Any bright ideas anyone?

Graeme
Graeme
 
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Re: Insufficient hot water for new bath

Postby John Gallon » Sun Sep 23, 2007 3:14 pm

Hi Graeme,
Another option would be a combi boiler but if you have low mains pressure it would still be a slow bath fill. You could either fit a larger capacity cold tank or depending on the space available fit another tank beside the existing, either way you will need a larger h/w cylinder. Once you have enough cold storage you could fit a pump to get greater flow/pressure.
John Gallon
 
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Re: Insufficient hot water for new bath

Postby Graeme » Sun Sep 23, 2007 7:00 pm

Thanks for that John.I'm coming round to the idea that a straightforward swop of cold and hot tanks is the answer (ie keeping the vented system) Your idea of pumping a tank sounds good.

Do you know if it would be feasible to add a second cylinder working alongside the existing one - rather than replacing the existing one with a bigger one? The trouble there is I'd need two coils and two vents back to the (same?)header tank. Not sure!

Graeme
Graeme
 
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Re: Insufficient hot water for new bath

Postby John Gallon » Mon Sep 24, 2007 9:07 am

Hi Graeme,
It would save a lot of complications to just have one larger cylinder rather than two smaller. You say you are short of space, is that in the airing cupboard or the loft? if you have enough space in the loft you could fit the cold tank and cylinder in the loft but the cold feed tank/s must be higher than the cylinder.
You loose heat in the airing cupboard but gain shelf space,
John
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Re: Insufficient hot water for new bath

Postby Graeme » Mon Sep 24, 2007 2:27 pm

Hi John

I'm actually short of space on both - well, height anyway. The U/S bedroom is within the roofspace with the CW tank above the ceiling at the small peak and the cylinder behind a wall in the triangular space at the eaves.

The CW supply could be increased by adding another one or two rectangular tanks of about 20 gallons each stretching the length of the peak and linked together. (I'm assuming this would be equally effective as a single large CW tank in terms of head)

The cylinder would be better replaced by a taller one downstairs, where there IS a space available - again, I'm assuming that it makes no difference where the cylinder is sited, provided the head from the CW tank is sufficient and the coil has a pumped feed from the boiler?

With the present head it would still take about 20 mins to fill the bath I reckon so perhaps I should think about adding a pump between the cylinder and bath. Does all that sound reasonable?

Many thanks for the advice.

Graeme
Graeme
 
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Joined: Tue Aug 28, 2007 10:43 am


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