moving hot water tank in loft

Postby crol » Mon Mar 10, 2008 5:36 pm

I am wanting to move my hot water tank from the bathroom into the loft. I have been advised that I have a one pipe system and that if I move the tank into the loft that I could have problems i.e. it might not heat up properly or worse not work. Is this correct?
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Simply Build It

Postby Kenj » Mon Mar 10, 2008 11:06 pm

Do not do this unless you want to experience problems such as these.

1. Low water pressure at shower.
2. Bath only filling a few inches with hot water.

The cold water tank needs to be above the hot water tank to provide an adequate flow of hot water. If is is not then the hot water pressure will be very weak, and the hot water from the cylinder may vent into the cold water storage tank instead of flowing into your bath.

The systems were designed with the cold water tank above the hot water cylinder for a good reason. But if you want a system that looks good rather than actually works, then go ahead and move the hot water cylinder.

FYI - the bottom of the cold water tank should be no less than 5 feet above the top of the hot water cylinder.
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Postby crol » Tue Mar 11, 2008 9:36 am

Thanks for the reply. So if I have it changed to a 2 pipe system will this improve things. I know of plenty of people with all the tanks in the loft with no problems. Are these likely to be 2 pipe systems?
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Postby Kenj » Tue Mar 11, 2008 11:44 pm

Hi crol,

No I experienced exactly the symptoms I described in my first property, and I had a two pipe system. The main problem is due to insufficient water pressure. The hot water flow to the taps relies on being pushed by the cold water in the cold water storage tank. The higher the cold tank is above the hot tank the greater this pressure is, resulting in a higher flow to the hot taps, shower etc. Also hot water from the cylinder could very easily rise up the open vent pipe and discharge into the cold tank rather than flow into your bath. An expensive waste and very irritating when you only get half a bath.

Have a look some of the other discussions on this topic.
The plumbing forum - thermostatic shower flow - for instance.
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Postby Charl » Mon Mar 17, 2008 12:43 pm

I asssume the two pipe system relates to the radiator feed but how was the hot water tank supplied?

Secondly I am moving an indirect copper cylinder on a 35,000 Bthu bolier with 3 way valve and two pipe sytem which is open vented for heating and cold water supply.

Propose to make the heating system sealed and the cold supply the same. Leave the pump and 3 way valve in the same position and put an 18 litre expansion, reduced in air pressure to about 0.2 to 0.3 bar to minimise pressure on the boiler and pipework on the return. Although the water expansion is only about 3 litres I want to minimise pressure variatiion, hence the larger expansion vessel.

I will raise the cold water tank but will not have 5 feet difference as discussed.

Any tips please?
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