water flow (plumbing)

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classic33

Leg End Member
Your biggest problem is it relies on air pressure & the weight of the water above the tap.
 

slowmotion

Quite dreadful
Location
lost somewhere
[QUOTE 4924400, member: 9609"]that is a nice little calculator and gives even better increase in flow rates that my earlier guess, I had guessed 2.89x based on cross sectional diameter of pipe
but that shows increasing pipe from 12 to 20 mm would give nearly 4x - which would be what I am look for.


How do you think it works if a pipe with two differant diameters are used. out of the 3m if 1m was 20mm and 2m was 25mm, would ou use the average of 23.3mm ? (that would give me nearly 6x the flow)[/QUOTE]
I'm no expert, but I suspect it very much depends on where the different pipe diameters are used, and what the head is at each section. There are online calculators that deal with such complexities, but they may not be freeware.

Here's some stuff on equivalent straight pipe lengths, page 78.....
file:///C:/Users/Martin/AppData/Local/Microsoft/Windows/INetCache/IE/X8D4VNMR/copper_tube_handbook.pdf
I'm sorry it's in imperial units. Scratch about and you'll find stuff in metric ones.
I'm always disappointed by estimates of fluid flow, whether liquid or gaseous. Just oversize everything!

Edit: Sorry, bad link. I'll try and find another.
 
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Location
Loch side.
[QUOTE 4924400, member: 9609"]

How do you think it works if a pipe with two different diameters is used. Out of the 3m if 1m was 20mm and 2m was 25mm, would ou use the average of 23.3mm ? (that would give me nearly 6x the flow)[/QUOTE]

It won't average out like that. To calculate total flow through a mixed system, you have to treat each section (diameter) as a separate section. Start with the flow it receives from the previous section.
If you can, design it so that the system tapers down from big to small, just like in your body.
 

sight-pin

Veteran
[QUOTE 4924383, member: 9609"]also ow much does a 90 degree bend restrict flow, my first go uses a 90 degree copper elbow, the poly pipe would have a much gentler arc[/QUOTE]

If you want a faster flow, don't use 90 degree elbows, use two 135 degree bends instead.
 

Cycleops

Legendary Member
Location
Accra, Ghana
I suspect you just don't have sufficient head of water in your container to provide enough pressure. This is my water storage tank and when above half full provides good pressure to the household taps that we don't need to use the electric pump.
IMG_0813.JPG

So if you can't get it up higher you need a bigger tank.
 

Cycleops

Legendary Member
Location
Accra, Ghana
Well it does!

Your best solution is to fit a small 'on demand' electric pump like the type they sell to boost the pressure for hand held bathroom showers.
 
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classic33

Leg End Member
I suspect you just don't have sufficient head of water in your container to provide enough pressure. This is my water storage tank and when above half full provides good pressure to the household taps that we don't need to use the electric pump.
View attachment 368961
So if you can't get it up higher you need a bigger tank.
Why's the tap at the bottom?
 

slowmotion

Quite dreadful
Location
lost somewhere
A bit sliding in sideways but.......couldn't you feed the rainwater from the roof (at a painfully slow rate) into your ponds, and then fill up your watering cans from the pond?
 
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