Pushfit flow rate

[21stcenturyelec]

Hi guys new to this forum so be gentle with me , we are building our own place and I'm looking to run a 22mm hot water loop.

The layout is:- at one end of the building is a HW cylinder in a Grd Flr Utility room with an ensuite above it and then 16m down the other end of the building is a Grd Flr Bathroom with another ensuite above this.

With me so far? right I'm going to run 3 legs of 22mm in the Grd Flr ceiling space from one end to the other, this is a 16m staright run, 2 legs will be the HW loop and the other leg will be the cold feed.

The question is, I want to run JG speedfit for the 16m legs then run copper at either end to the various tap and shower points, I'm concerned that once I fit the insert to the JG pipe the bore is reduced to about 17mm will this give me a problem with the flow/presure to 3 bathrooms?

Phew!! got there in the end. By the way if it helps, the mains presure here is mega, I've not tested it but i'd guess it well over 3.5bar.

 

[Puddle]

Well if you are doing a self build and all that it involves,I would love to see the detail of other things, if you have raised concern about any restriction though a insert fitted
Especially as I doubt you have considered or calculated if the 22mm plastic pipe run will be adaquate to supply your demands and not cause restrictions in itself
However in answer to the quesion inserts fitted in joints will not restrict any flow at outlets,the restriction through the outlet itself may however

 

[21stcenturyelec]

Well if you are doing a self build and all that it involves,I would love to see the detail of other things, if you have raised concern about any restriction though a insert fitted
Especially as I doubt you have considered or calculated if the 22mm plastic pipe run will be adaquate to supply your demands and not cause restrictions in itself
However in answer to the quesion inserts fitted in joints will not restrict any flow at outlets,the restriction through the outlet itself may however

In terms of detail its as per the 1st post there are 3 bathrooms a Utility. the only addition is a small demand from the the kitchen and one wc, but the key thing is the 3 bathrooms, but the chances that they will run at the same time is slim.

No I've not done any calcs on the system and I've assumed rightly or wrongly that 22mm would be more than enough as the main MDPE is 25mm and the Nibe VPA cylinder has a 22mm feed and 22mm outlet and I also assumed if my HW is mains fed, then I was already asking the 25mm incomer to feed a total of 44mm across the hot and cold bores.

HW is a 300/200 VPA fed by a GSHP and a 150ltr pre-heat cylinder heated by solar panels total HW capacity is 285+150ltr.

Each bathroom will have a mixer shower, sink and toilet.

What is the formula for this if you let me know I can do the maths, thanks

 

[Bernie2]

There are so many points to consider here I'll have to try and answer them one at a time.

I know for instance that your going to run 22mm hot in a ceiling space above the Grd floor area. I assume its an ordinary situation with floor boards for the floor above?

In the water Regs any run of 22mm hot has got to be insulated if its longer than 12m.

The recommended storage of hot water, is for about 140 litres per three person household. So one assumes your talking about 3 households or 9 people?

Which is obviously 420 litres.

So your 300/200 litre VPA plus 150 litres solar cylinder seems okay.

I thought the VPA 300/200 is shown having 28mm hot outlet and 28mm cold feed not 22mm?

Reducing a 22mm pipe to a 17mm is bound to cause restriction, it all depends will it be to much. I'll try and work something out to get an idea.

I'll try not to give you an off the cuff opinion, but try to back it up with sources so you can check what is written.

 

[anz]

Let me google that for you

 

[21stcenturyelec]

There are so many points to consider here I'll have to try and answer them one at a time.

I know for instance that your going to run 22mm hot in a ceiling space above the Grd floor area. I assume its an ordinary situation with floor boards for the floor above?

In the water Regs any run of 22mm hot has got to be insulated if its longer than 12m.

The recommended storage of hot water, is for about 140 litres per three person household. So one assumes your talking about 3 households or 9 people?

Which is obviously 420 litres.

So your 300/200 litre VPA plus 150 litres solar cylinder seems okay.

I thought the VPA 300/200 is shown having 28mm hot outlet and 28mm cold feed not 22mm?

Reducing a 22mm pipe to a 17mm is bound to cause restriction, it all depends will it be to much. I'll try and work something out to get an idea.

I'll try not to give you an off the cuff opinion, but try to back it up with sources so you can check what is written.

Cheers Bernie2, Yes you’re right on the 28mm, my mistake.

What I will do is run in 28mm to just above the tank then split it using a 28x22x22. One leg of 22mm will go to the 16m run catering the 2 baths down the far end. The second will be a local loop covering the 3rd bath, utility and kitchen.

The insulation I’ve ordered is the 13mm walled stuff is that OK? the ceiling make up will be Plasterboard. Pipe work, 100mm Rockwool, bubble foil, UFH on clippa plate and then chipboard deck.

My misses will use that 140ltr’s in one shower, its like the Hanging Gardens of Babylon in the bathroom when she gets done.

The house could be configured as a 6/7 bed so we want to make sure it’s done to handle a bigger family than we have. We will only use it for 4 us + 4 family/visitors.

Since posting the thread on here I’ve talked myself into going copper all the way so would your gut feeling be that this resolves any issue with the reduction caused by plastic?

Thanks for your positive input on this

 

[21stcenturyelec]

Let me google that for you

 

[Bernie2]

Yes! Perhaps 21st Century

One of the points is about pipe sizing, flow and velocities.

Obviously your tied to 28mm for your initial size, but it will also depend where you take the tees out for the fittings, how good the rest of the system gets supplied.
In other words even if you have a mains fed unvented cylinder at about 3 bar (30 metres head) pressure it doesn't mean you can necessarily use it all. Putting it simply, there is a maximum BS6700 recommended velocity of 3 metres per second in 22mn cold water copper pipe, where higher velocity can cause excess erosion and noise in the pipe work. To prevent it, you go to the next size up.
So there are limit's that you have to work out.

Speedfit say their limits are roughly the same as copper pipe, so what the copperboard site says applies to plastic as well.

I would suggest having a look at the UK Copper board web site on pipe sizing. Its a mine of good info.

They do a good download and even a Webcast which covers many of the points you raise and a few more. You will probably find out from there, why its not so easy to give an off the cuff answer. You will also find all the info to work your sizes out. Main thing is its free!

The recognised BS6700 costs a bomb unless your library gives you free access to it.

But a lot of the info on the copperboard site seems to agree with it.

Hope this helps.

 

[21stcenturyelec]

Yes! Perhaps 21st Century

One of the points is about pipe sizing, flow and velocities.

Obviously your tied to 28mm for your initial size, but it will also depend where you take the tees out for the fittings, how good the rest of the system gets supplied.
In other words even if you have a mains fed unvented cylinder at about 3 bar (30 metres head) pressure it doesn't mean you can necessarily use it all. Putting it simply, there is a maximum BS6700 recommended velocity of 3 metres per second in 22mn cold water copper pipe, where higher velocity can cause excess erosion and noise in the pipe work. To prevent it, you go to the next size up.
So there are limit's that you have to work out.

Speedfit say their limits are roughly the same as copper pipe, so what the copperboard site says applies to plastic as well.

I would suggest having a look at the UK Copper board web site on pipe sizing. Its a mine of good info.

They do a good download and even a Webcast which covers many of the points you raise and a few more. You will probably find out from there, why its not so easy to give an off the cuff answer. You will also find all the info to work your sizes out. Main thing is its free!

The recognised BS6700 costs a bomb unless your library gives you free access to it.

But a lot of the info on the copperboard site seems to agree with it.

Hope this helps.

Bernie you have been a great help on this and I'll look at the copperboard site. Many thanks again Ian

 

[justlead1]

Hi, When you mention 22 mm loop is this a pumped secondary return?

 

[21stcenturyelec]

Hi, When you mention 22 mm loop is this a pumped secondary return?

If you mean does it go out and then re-enter on the extra pipe supplied at the top of the tank then yes. It goes out in 22mm and retruns in 15mm and it is pumped by a bronze pump.