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15mm rising main to 4 apartments?

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dan_the_plumber

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Hi
I’m currently working on a 3 story house that’s being converted into 4 flats. I installing 40kw boiler, 15 rads, 4 Heating zones plus a hot water zone. Etc etc
Each flat has a kitchen sink, toilet, basin and electric shower.
Problem is, I’ve got a 15mm rising main. ‭Im hoping it’ll just be adequate.
However as back up I’ve thought about installing a booster set.
As a back up to the back up I’ve thought about installing a break cistern then a booster set.
I wondered if you had some experience and thoughts on this?
I’m sort of dreading telling the client that he needs a 25mm rising main, especially when the main also supplies 2-3 buildings. Thanks...Dan
 
dan_the_plumber said:
Hi
I’m currently working on a 3 story house that’s being converted into 4 flats. I installing 40kw boiler, 15 rads, 4 Heating zones plus a hot water zone. Etc etc
Each flat has a kitchen sink, toilet, basin and electric shower.
Problem is, I’ve got a 15mm rising main. ‭Im hoping it’ll just be adequate.
However as back up I’ve thought about installing a booster set.
As a back up to the back up I’ve thought about installing a break cistern then a booster set.
I wondered if you had some experience and thoughts on this?
I’m sort of dreading telling the client that he needs a 25mm rising main, especially when the main also supplies 2-3 buildings. Thanks...Dan
Click to expand...

I think you've hit the nail on the head with the tank and pump set.

How high is the Building and what is the Static pressure at ground level?
 
Won't work on just mains if your right at the top be around a bar loss
 
Last Plumber said:
I think you've hit the nail on the head with the tank and pump set.

How high is the Building and what is the Static pressure at ground level?
Click to expand...

Thanks s lot :) well I’ve got 2.5 bar at ground, then top outlet is about 7 M up. So I recon 0.7 Bar loss. Minus equivalent pipe length, minus fittings.

Thing is there’s really no chance of having mains pipe re-run in 25mm. So you recon a break cistern and booster set is way to go then?
 
dan_the_plumber said:
Thanks s lot :) well I’ve got 2.5 bar at ground, then top outlet is about 7 M up. So I recon 0.7 Bar loss. Minus equivalent pipe length, minus fittings.

Thing is there’s really no chance of having mains pipe re-run in 25mm. So you recon a break cistern and booster set is way to go then?
Click to expand...

Can you get 22mm pipe upto the flat ?
 
Whats supplying the hot water?
Is there a plant room where the boiler etc are going?
 
Does the 15mm main do all property's or just that one flat ?
 
dan_the_plumber said:
Thanks s lot :) well I’ve got 2.5 bar at ground, then top outlet is about 7 M up. So I recon 0.7 Bar loss. Minus equivalent pipe length, minus fittings.

Thing is there’s really no chance of having mains pipe re-run in 25mm. So you recon a break cistern and booster set is way to go then?
Click to expand...
I do think you are best with that set up but you will need to increase the size of the riser anyway in my opinion.
Personally, I would use 22 mm Copper, it needs calculating though.
The 15mm would be too restricted and noisy. (if that is what you are thinking)
 
Last Plumber said:
I do think you are best with that set up but you will need to increase the size of the riser anyway in my opinion.
Personally, I would use 22 mm Copper, it needs calculating though.
The 15mm would be too restricted and noisy. (if that is what you are thinking)
Click to expand...

Thanks for advise. Yeah I was thinking of running all cold pipe work from outlet of booster set pump in 22mm. Then reducing down to 15mm say 2M before appliances.

Does that sound right to you? Thanks :)
 
dan_the_plumber said:
Thanks for advise. Yeah I was thinking of running all cold pipe work from outlet of booster set pump in 22mm. Then reducing down to 15mm say 2M before appliances.

Does that sound right to you? Thanks :)
Click to expand...

Thought you said you couldn't get 22mm upto the flat ?
 
15mm will definately not do three apartments bud you can only get out what you put in 15mm wont even do the unvented cylinder you need a re think . kop
 
king of pipes said:
15mm will definately not do three apartments bud you can only get out what you put in 15mm wont even do the unvented cylinder you need a re think . kop
Click to expand...

No. But I’m thinking of break cistern then booster set. 22mm jp through building then reducing down a meter or two before appliances. What do you think?
 
yea you will be ok if you only have 15mm into the break tank just need to size it so it can cope with peak demand and then 28mm into the pump from the tank and then 22mm to the flat

will the pump supply the whole building?
 
You will need to boost it somehow bud your probably on the right track i would be covering my arse and telling the client your conserns about it being under sized put it in writing just in case of problems down the line. Cheers kop
 
ShaunCorbs said:
yea you will be ok if you only have 15mm into the break tank just need to size it so it can cope with peak demand and then 28mm into the pump from the tank and then 22mm to the flat

will the pump supply the whole building?
Click to expand...

Well I suppose the pump will do all of the DHW (through unvented cylinder) Then I suppose it’s only really got to do cold water for upstairs flats.

Only other thing I’m wondering...Presumably the booster pump will also need a small accumulator. This, just to start the pump running when a tap upstairs is opened?
 
TWS contact them bud heres one thats been in 6years 20mm supply in and does 2 properties . kop

Screenshot_2018-03-22-06-21-40.png


Screenshot_2018-03-22-06-21-45.png
 
I would be boosting all hot and shower cold
Run a main in to do the kitchen and bathroom basin cold for drinking water. This will still work when ther is no power, keep drinking water safe and reduce the size of your break tank.
 
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 :)
 
Last edited:
DevsAd said:
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 :)
Click to expand...

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?
 
dan_the_plumber said:
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
Click to expand...

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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