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https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl DIY Forum >> Plumbing Questions >> Domestic hot water https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl?num=1103674189 Message started by spongebob on Dec 22^nd, 2004, 12:09am

Title: Domestic hot water
Post by spongebob on Dec 22^nd, 2004, 12:09am

Is there a way to increase the pressure to the tap outlets on a gravity domestic hot water system. I assume that a shower pump would be unsuitable for this.

Title: Re: Domestic hot water
Post by spongebob on Dec 22^nd, 2004, 12:11am

......other than mounting the hot water tank on a tower above the house. Thought I'd get that in before someone else did.

Title: Re: Domestic hot water
Post by Stoday on Dec 22^nd, 2004, 12:11am

Increase the height of the HW feed cistern.

Title: Re: Domestic hot water
Post by Stoday on Dec 22^nd, 2004, 12:12am

Ya just made it Spongebob!

Title: Re: Domestic hot water
Post by spongebob on Dec 22^nd, 2004, 12:14am

Stoday.....would only gain about 1200mm from present position. can't imagine that doing to much to increase the pressure.

Title: Re: Domestic hot water
Post by spongebob on Dec 22^nd, 2004, 12:15am

Hell....you got to be quick round here!!

Title: Re: Domestic hot water
Post by bstyle on Dec 22^nd, 2004, 12:16am

I assume you want to increase the cold pressure also?

You can fit a whole house pump this will pump both the h + c.

Or possibly look into getting a single impeller pump for the hot

Title: Re: Domestic hot water
Post by Stoday on Dec 22^nd, 2004, 12:22am

Spongebob -

We don't know enough to say if it would or wouldn't.

My guess is that the problem is his bath tap. Maybe 2400mm below the cistern's water level. Increasing the height 1200mm would increase the pressure at his bath tap by 50%.

Of course, it may be a downstaris tap; he may have a bungalow; he may have enough roof space to gain more than 1200mm.

Title: Re: Domestic hot water
Post by bstyle on Dec 22^nd, 2004, 12:29am

I had a job recently where I put a coffin tank in right at the top of the pitched roof, made a huge difference in pressure - no need for shower pump in upstairs bathroom

Title: Re: Domestic hot water
Post by spongebob on Dec 22^nd, 2004, 12:54am

Sister-in-laws house. She has a bungalow. She's looking to refurb both her bathrooms and is having a devil of a time with plumbers either not turning up or getting back to her. That aside most of the taps she's looking at require a minimum of 1.0 bar. Not sure what her existing pressure is but the hot barely trickles out of her taps. I said I'd make some enquiries. However if she'd listened to me in the first place and installed a combi we wouldn't be having this discussion.

Title: Re: Domestic hot water
Post by bstyle on Dec 22^nd, 2004, 12:57am

What area?

Title: Re: Domestic hot water
Post by Stoday on Dec 22^nd, 2004, 1:30am

For 1.0 bar you need a head of 10 meters.

You won't get that for a gravity system in a bungalow.

Title: Re: Domestic hot water
Post by JerryD on Dec 22^nd, 2004, 7:26am

The only options are:

1) Single impeller pump on both hot and cold feeds, or

2) Only buy 'low pressure' taps, or

3) Raise cw tank in loft as much as possible, or

4) Low pressure taps AND raise cw tank in loft, or

5) Combi or System boiler (Megaflow type), and/or

6) Convert bungalow to a two storey house with steep roof ::)

Title: Re: Domestic hot water
Post by bstyle on Dec 22^nd, 2004, 10:23am

Interested to know why you would need a single imp. pump on hot and cold instead of 1 twin pump?

Title: Re: Domestic hot water
Post by JerryD on Dec 22^nd, 2004, 5:47pm

so that you can run just one tap at a time. Twin impeller pumps don't like having one side 'shut' while the other side runs.

I have spoken to Stuart Turner about this point, their twin impeller pumps have 'slippage' built into them for just this type of situation but continual use of just hot or just coold will wear the pump quicker.

Therefore, for baths and basins it is better to pump the hot separately and the cold separately. Showers, on the other hand, nearly always run both supplies together so a twin impeller pump is ideal for showers. (unless you like long cold showers every morning and night? ::))

;D

Title: Re: Domestic hot water
Post by bstyle on Dec 22^nd, 2004, 6:48pm

Interesting point,

Stuart turner dont make a seperate pump for whole house situations, a lot of other brands eg. salamander do make 2 types, in the past I contacted stuart turner about swapping a salamander shower pump (which was pumping whole house) to a S.T twin and they said this was O.K to use.

I suppose they're not going to advertise the fact that the twin pumps aren't really designed for complete pumping.

I'll keep it in mind not to use stuart turner twins for fully pumped supplies.

Thanks

Title: Re: Domestic hot water
Post by thescruff on Dec 22^nd, 2004, 7:05pm

I would always use two single pumps for whole house installations.

Like the comment about combi can, reakon she would have disowed you by now with one m8 ;D

scruff

Title: Re: Domestic hot water
Post by spongebob on Dec 22^nd, 2004, 11:23pm

Single impeller pumps.....electrics and flow switches I imagine. That's me helping her down the pan (no pun intended). Like a typical women she's doing everything a**e about face. The heating and hot water system is ancient and in my opinion should have been one of the first jobs to be done whether with a combi installation or something else. However she's just spent a vast sum of money having fancy flooring laid throughout the house and now she's on about getting the bathrooms done. I know that in the end she'll do what she wants, but she's family and on her own with 2 kids and I get it in the neck if I don't chip in.