Poor pressure from combi boiler

[Koko]

Hello, I hope someone can help (first post so hopefully I will give you all the info needed!)
I am having problems with the water pressure in my house. I have a combi boiler - Worcester 24i, don't know how old. When I use the bath tap shower it keeps going cold, i live on a little terrace and have spoken to the neighbours who are having the same problem. I called three valleys water and they said that the water pipes cant cope with 12 houses on one supply using boilers ??? They would provide a new connection but i would have to get the pipes fitted to my house, not possible as i am six houses away from the main road so would cost far to much. I was wondering if it is possible to fit a water tank in the loft just for an electric shower.
Thanks

 

[Agile]

Its a little difficult getting a proper figure for the pressure and flow which they MUST supply.

Three Valleys seem to be one of the WORST in the London area!

When I made a similar enquiry in the midlands area I was told that their minimum open pipe flow was 6 litres per minute and the static pressure was a minimum of 0.6 bar at zero flow. Thats pretty poor! Thats at ground floor level too!

You can fill a lot of loft storage overnight and then pump it to get proper pressure and flow.

Standard loft storage is about 200 li. If your supply is dire then two or three times this capacity might be needed. Professional cost to install about £700.

Tony Glazier

 

[ChrisR]

I think 3 Valleys use 7's instead of Tony's 6's - still dire!

Quite a few top floor flats in London have a biggish cistern with a pump feeding a combi and cold to a shower. LAst one I saw only had a 50 gallon tank and that could run out on occasion, with only one person using it. Bears out Tony's figures.

Make sure the walls can hold it up then put lots of spare capacity in so you can sell it to your neighbours!

 

[simond]

Hello Koko

If your static pressure is over 1.5bar you could fit an accumulator, which will solve your problem.

Your water supplier can usually give you the design pressure over the phone - it's the flow rate they don't like discussing.

The accumulator is a cylinder approx 535mm round and will 'accumulate' water at pressure so that it can discharge at a massive flow rate when you take a shower etc. It will also buffer you from other users in your vicinity using the water main at the same time, which is clearly a problem.

We often fit combis with this device where the flow rate is poor, or if a customer wants a 'fast' combi (eg: WB Highflow 440 or a Vaillant 837) but hasn't enough water.

We can't help you in Hertfordshire (it's outside our installation area) but if you email me i can put you in touch with the manufacturer, or maybe someone else in the trade on this forum can arrange it.

Finally, there is a regular correspondent on this forum who says accumulators can't work and they are a con. He is hydraulically challenged and best ignored! 10,000 have been sold to date.

 

[Koko]

Hi all
thanks for all your advice. I will contact three valleys to try to get the relivant info, and hopefully get the shower sorted!
Koko

 

[ChrisR]

WHat volume accumulator would you suggest here Simon?

 

[simond]

Hello Chris

I'd suggest a 310 litre nominal, which equates to about 150 - 180 litres usable (depending on static pressure).

If there's only one person in the property, or two people sharing but not running one large bath 10mins after the other, a smaller one will fit the bill, say 240 litres nominal..........

Trouble is, you give people a much better flow rate for showers and of course they use more water. Had a customer today with an unvented accumulator set up who drained a 450 litre in less than an hour - teenage daughters.