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15mm rising main to 4 apartments?
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View the thread, titled "15mm rising main to 4 apartments?" which is posted in UK Plumbers Forums on UK Plumbers Forums.
Tws have gone / been eaten by Stuart turner
Hi Dan.
Can you confirm, please: for these 4 flats you are "installing a 40kw boiler, 15 rads, 4 Heating zones plus a hot water zone. Each flat has a kitchen sink, toilet, basin and electric shower" - so that's two hot and four cold outlets in total in each flat?
And the boiler and unvented hot cylinder are going in a plant room?
I'm not a plumber, but have been looking in to boosting cold mains supplies recently, so may have some points that might help.
Your plant room will have a single hot cylinder to provide hot water to all 4 flats, essentially to two taps in each one? What size hot cylinder is this?
I think the solution to your problem could be as easy as a pumped accumulator as mentioned by yourself above, tho' probably a much larger size - 300 litres plus. There are a number of models to choose from like the Stuart-Turner you mentioned or the Challis CB+450 ( Challis Booster ) or Grundfos (more costly) or the BoostaMain (very much more costly...) equivalents.
I've spoken to the boss of Challis and was impressed by the spec. The outlet from this system can be as large as 28mm, so I understand that can deliver the stored supply at a crazy rate of around 100 lpm at 3 bar should it be required (which, of course, it won't), but this would surely supply the hot cylinder and colds to the 4 flats nicely? (And the big plus of the Challis model, I've been told, is that the accumulator's stored water outlet goes directly out to the building's supply, and doesn't pass back through the pump like on some designs.)
I think it can even store and supply water at up to 4.5 bar tho' 3 bar would be the most usual setting. In the unlikely event that you find that 450 litres isn't enough capacity (some git leaves their tap running...) then an extra accumulator can be added which would operate off the same pump, so little extra cost. If it ever did run out, then it'll still draw the cold mains at the max 12lpm rate to keep a supply going. And the price of the CB+450 is, I think, only around the £1k mark?
The really nice thing about these pumped accumulators is the way the (3bar) pressure is stored so that it is then released to the outlets in exactly the same natural manner as a normal mains supply. Ie: the stored 3bar delivers the water smoothly from the moment you creak open a tap; you don't have an initial pitiful trickle followed by a pump kicking in as you would with pumped flows.
If you work out the rough max flow requirements for each flat and then contact Challis and others and put your issue to them, you should hopefully have a good idea whether it's the answer. If it is, then it should be cheap and reliable.
Oh, and since these systems are air-sealed, I have been told that they are effectively like just a 'very large supply pipe', so the water passing through is still potable and WRAS approved - so they can supply ALL the taps with drinking water with no need to have a separate mains supply to the kitchen cold 🙂
Can you confirm, please: for these 4 flats you are "installing a 40kw boiler, 15 rads, 4 Heating zones plus a hot water zone. Each flat has a kitchen sink, toilet, basin and electric shower" - so that's two hot and four cold outlets in total in each flat?
And the boiler and unvented hot cylinder are going in a plant room?
I'm not a plumber, but have been looking in to boosting cold mains supplies recently, so may have some points that might help.
Your plant room will have a single hot cylinder to provide hot water to all 4 flats, essentially to two taps in each one? What size hot cylinder is this?
I think the solution to your problem could be as easy as a pumped accumulator as mentioned by yourself above, tho' probably a much larger size - 300 litres plus. There are a number of models to choose from like the Stuart-Turner you mentioned or the Challis CB+450 ( Challis Booster ) or Grundfos (more costly) or the BoostaMain (very much more costly...) equivalents.
I've spoken to the boss of Challis and was impressed by the spec. The outlet from this system can be as large as 28mm, so I understand that can deliver the stored supply at a crazy rate of around 100 lpm at 3 bar should it be required (which, of course, it won't), but this would surely supply the hot cylinder and colds to the 4 flats nicely? (And the big plus of the Challis model, I've been told, is that the accumulator's stored water outlet goes directly out to the building's supply, and doesn't pass back through the pump like on some designs.)
I think it can even store and supply water at up to 4.5 bar tho' 3 bar would be the most usual setting. In the unlikely event that you find that 450 litres isn't enough capacity (some git leaves their tap running...) then an extra accumulator can be added which would operate off the same pump, so little extra cost. If it ever did run out, then it'll still draw the cold mains at the max 12lpm rate to keep a supply going. And the price of the CB+450 is, I think, only around the £1k mark?
The really nice thing about these pumped accumulators is the way the (3bar) pressure is stored so that it is then released to the outlets in exactly the same natural manner as a normal mains supply. Ie: the stored 3bar delivers the water smoothly from the moment you creak open a tap; you don't have an initial pitiful trickle followed by a pump kicking in as you would with pumped flows.
If you work out the rough max flow requirements for each flat and then contact Challis and others and put your issue to them, you should hopefully have a good idea whether it's the answer. If it is, then it should be cheap and reliable.
Oh, and since these systems are air-sealed, I have been told that they are effectively like just a 'very large supply pipe', so the water passing through is still potable and WRAS approved - so they can supply ALL the taps with drinking water with no need to have a separate mains supply to the kitchen cold 🙂
Last edited:
dan_the_plumber
Gas Engineer
Hi. That is incredibly helpful if you, Thanks!
Actually since posting on here I have been in touch with Stuart Turner and have completed a site survey taking static and working pressures etc.
I will speak to them Monday and they should be able to recommend a suitable product. I’m hoping I can just go for a mains boost accumulator without a pump.
Once I know what to go for the I can look at price and will compare with the Challis products.
Your points about stored potable water are very interesting. In fact I hadn’t quite got to thinking about that, but now will definitely take that into account.
Thanks again for your help
What's the pressures and flow static and dynamic?
There is a large difference between pumped and non-pumped accumulators. The latter relies wholly on the existing water pressure for its delivery performance, and if you reckon that will be only be at around 1.5+ bar at the top flat, then I don't think it's going to be successful. Also, lower flats will affect the performance of the higher ones if they are all drawing simultaneously. Unpumped accumulators are ideal for when the mains pressure is good - 3+ bar - but the incoming flow rate is low.
The pumped models aren't that much more costly, and there is no 'pump effect' to the way they work as far as the flats are concerned; the pump only fires up when it needs to to recharge the accumulator. The pressurised accumulator itself does all the water supplying to the properties, and this can be at a very impressive flow rate and driven by a guaranteed pressure.
It will be interesting to see what ST come up with. I'd thoroughly recommend contacting Challis and Grundfos too - there are some differences.
In an ideal world bud but the op has said not much chance of a new main upgrade . kop
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