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Thread: Pressured Pipe Sizing Basics
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18-07-2021, 02:00 PM #1
Pressured Pipe Sizing Basics
Hi all, thought this might be useful for anyone who is unsure what pressure pipe systems size they need..
The first step is to decide what pipe size you need, based on pump flow rate (at zero head as per general pump information)..
https://www.kwangu.com/work/pipesize.htm
- Add mass or volume flow rate at top (1 litre of water = 1 kg so both boxes are the same value)
- Estimate pipe size in UPVC - class C material box.
- Calculate.
You then need to check the Results figures at the bottom and try to keep within following limits..
- Pressure drop per unit length - 150 - 300Pa/m (definitely no more than 400Pa/m)
- Velocity - 0.8 - 1.5m/s
You don't need to worry about the other figures if these are within max parameters. If they exceed the parameters, increase selected pipe size and re-calculate. Repeat until the parameters are correct and that will be your pipe size. If cost is a concern, it can pay to play around with the pipe sizes to determine the most cost effective solution.. a smaller size system (say 65mm instead of 80mm) is quite a bit cheaper but will reduce flow rate due to pressure increases.
Once that is done, the pressure loss of the piped system ( head loss) can be calculated.. this is as good as any for pond system calculations..
https://www.plasticpipeshop.co.uk/Fl...r_ep_60-1.html
- Input the pipe size from above and flow rate.
- Add pipe lengths and number of fittings.
- Calculate.
This will give you a total head pressure loss of the pressured pipework system. It is important now to add the static head (the distance from the lowest point of the water system to the highest) to the pipe system pressure. The total can then be used on the manufacturers pump curves to give you the actual flow rate you will get out of the pump.
Please note that this is for the pipework systems only and does not account for pressurised filters. Some manufacturers may provide pressure filter head loss figures (which you can add to the total pressure loss, but as with all filters the pressure loss increases as they get dirty). This also applies to the filter screens around submersible pumps.
I'm sure plenty of you know all this but hope it might help some people out.
Last edited by Point; 18-07-2021 at 02:03 PM.
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davethefish1, Mannh85 Thanked / Liked this Post
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18-07-2021, 02:07 PM #2
This might also be useful to determine actual flow rate..
https://www.watergardeningdirect.com...Of-A-Pump.html
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davethefish1 Thanked / Liked this Post
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18-07-2021, 02:53 PM #3
the first one to me seems quite complicated...but still useful.
like really the headloss calc good one for seeing how much changing pipe diameter helps increase flow rate
one thing regarding pressure pipe, that i have always found in over 30 years of pipefitting.
buy the pipe and fittings from the same manufacturer. all sizes are not the same fit.
the 4" pipe i have recently bought from coastal koi fit the fittings perfectly and easily both dry when marking out, and glues up solid with no gaps.
just bought an extra 3mtrs of 4" locally and i can only get it a quarter of the way in dry, and will probably struggle to get the pipe seating all the way in when glued up.
and can even be so tight it pushes the pipe back out of the fitting when you let go....this in my experience is a major factor for leaks.
i'll have to belt sand the pipe all round where i'm jointing it, to make sure it goes fully home when glueing up...
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Point Thanked / Liked this Post
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18-07-2021, 04:15 PM #4
It might seem complicated Dave but it just looks that way because of all the different pipe materials options. It's a programme for various types of pipe systems used in mechanical building services for hot and cold water using different temperatures but it's only flow rate, pipe size, pressure drop/m and velocity that anyone needs to worry about.
You're absolutely right about pipe sizes being slightly different between manufacturers.. they often work to different tolerances and even a small variation can cause problems. The problem is exacerbated with temperature changes in summer and winter.Last edited by Point; 18-07-2021 at 04:18 PM.
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davethefish1 Thanked / Liked this Post
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