Do any of you know where I can get a list of the max flow rates through pipework under gravity. Or, even better, a formula that will calculate it. All I can find is a Manning formula that returns very optimistic flow rates or various rough flow rates quoted on various sites for 4" pipe.
I am designing something and need to know how many pipes of different diameters I would need to return the flow from a shower under gravity. I'm hoping to use multiple 2", 3", 50mm or 63mm pipework and need to know how many of the various sizes I would need to work out the best solution.
Cheers,
Ed.
Flow rates for gravity feed
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Re: Flow rates for gravity feed
hi Ed
PM me your email address and I'll send you a word.doc with a forula.
Not keeping it secret, but don't know how to include square root symbols etc. on the forum!
If anyone else wants it, PM me your email address - or can anyone tell me how to copy a word document into a post??
Cheers
Bob
PM me your email address and I'll send you a word.doc with a forula.
Not keeping it secret, but don't know how to include square root symbols etc. on the forum!
If anyone else wants it, PM me your email address - or can anyone tell me how to copy a word document into a post??
Cheers
Bob
Re: Flow rates for gravity feed
Cheers Bob, PM just sent.kayoss wrote:hi Ed
PM me your email address and I'll send you a word.doc
Cheers
Bob
Ed
Re: Flow rates for gravity feed
Hi Ed
you should have email mate!
Cheers
you should have email mate!
Cheers
Re: Flow rates for gravity feed
I have mate, cheers.
I'm going to set that formula up on a Excel sheet to calcuate the flow rates for different diameters and will post the figures on here in case anyone else needs them. That's if I get sensible answers of course!!!!
I'm going to set that formula up on a Excel sheet to calcuate the flow rates for different diameters and will post the figures on here in case anyone else needs them. That's if I get sensible answers of course!!!!
Re: Flow rates for gravity feed
Right, after getting some very, very odd results I realised where I'd gone wrong with Bob's formula and got it to work!
NB. I've reduced the diameters of the pipe down to 25mm per inch to take account of the thickness of the pipe walls and it made sense to under-estimate rather than over estimate.
Do these flow rates look ok to you guys? I've had to calculate the pressure from the 4" pipe to extrapolate the others.
NB. I've reduced the diameters of the pipe down to 25mm per inch to take account of the thickness of the pipe walls and it made sense to under-estimate rather than over estimate.
Do these flow rates look ok to you guys? I've had to calculate the pressure from the 4" pipe to extrapolate the others.
Re: Flow rates for gravity feed
Hi Ed
Are these flow rates with no head loss?
My shower is remote from the pond and has a single 4" return and has more than 20,000L/hr over it, but has a 500mm head on the pond.
Dave
Are these flow rates with no head loss?
My shower is remote from the pond and has a single 4" return and has more than 20,000L/hr over it, but has a 500mm head on the pond.
Dave
Re: Flow rates for gravity feed
Yeah these will be with zero head.Davej wrote:Hi Ed
Are these flow rates with no head loss?
My shower is remote from the pond and has a single 4" return and has more than 20,000L/hr over it, but has a 500mm head on the pond.
Dave
You get 20,000lph with a 500mm head? How do you connect the shower to the pipework? Do you have a collection hopper from the shower? I'm just asking as this is what I'm planning, a shower feeding into a hopper with mulitple pipe returns to the bottom of the pond for circulation.
Re: Flow rates for gravity feed
Hi Ed
I will measure the exact head tomorrow but no more than 500mm.
Mine is simple standard bottom tray with 4" outlet built in, two spraybars each fed from aquamax 16000 via 2" pipe. Single return is 5m long so gets some frictional loss and returns at 1m depth. I get about 50mm back up in the bottom tray.
Mike at Yume stocks them, his main pond showers are remote so is the Guy to talk to My take is the design could be improved on with a funnel rather than a straight flange, with the standard flat base I get some air being drawn into the return but this will be sorted this spring and then I will push a bit more over there.
The bigger the pipe the better, avoids the extra frictional losses you get with multiple smaller pipes.
Dave
I will measure the exact head tomorrow but no more than 500mm.
Mine is simple standard bottom tray with 4" outlet built in, two spraybars each fed from aquamax 16000 via 2" pipe. Single return is 5m long so gets some frictional loss and returns at 1m depth. I get about 50mm back up in the bottom tray.
Mike at Yume stocks them, his main pond showers are remote so is the Guy to talk to My take is the design could be improved on with a funnel rather than a straight flange, with the standard flat base I get some air being drawn into the return but this will be sorted this spring and then I will push a bit more over there.
The bigger the pipe the better, avoids the extra frictional losses you get with multiple smaller pipes.
Dave
Re: Flow rates for gravity feed
Cheers Dave. I'll chat to Mike about it when down at Maurice's at some point hopefully! If he doesn't see me coming! 
I'm planning a shower in a streamflow pond using the flow from the shower to feed to 4-6 pipes that will exit at the bottom of the pool to create a current that will wash the dirt down the bottom to the uplifts. I need the multiple pipes to spread the flow over the whole width of the pond so will have to take a little extra friction to get that!
I've done some calculations based on your flow rate and reckon you have a pressure about 6 times that of the normal zero head gravity flow, but still only 0.003 bar! I'm planning a wide and long fibreglass shower that will fall into a shaped fibreglass hopper that will reach to about 12" above the pond level and will be shaped down to the outlets so that nothing can settle out in the hopper.
I'm planning a shower in a streamflow pond using the flow from the shower to feed to 4-6 pipes that will exit at the bottom of the pool to create a current that will wash the dirt down the bottom to the uplifts. I need the multiple pipes to spread the flow over the whole width of the pond so will have to take a little extra friction to get that!
I've done some calculations based on your flow rate and reckon you have a pressure about 6 times that of the normal zero head gravity flow, but still only 0.003 bar! I'm planning a wide and long fibreglass shower that will fall into a shaped fibreglass hopper that will reach to about 12" above the pond level and will be shaped down to the outlets so that nothing can settle out in the hopper.
Re: Flow rates for gravity feed
Hi Eds
Got the tape out - 400 to 450mm head on mine from pond level (min max).
My take is that If you are going for multiple small pipes then do give yourself scope for the frictional losses.
Dave
Got the tape out - 400 to 450mm head on mine from pond level (min max).
My take is that If you are going for multiple small pipes then do give yourself scope for the frictional losses.
Dave
Re: Flow rates for gravity feed
Cheers Dave, will do. I've got a bit more info from Bob that will help calculate the head caused by different pressures so I'll be able to work out the head caused by certain numbers of different pipes to give me a good margin of error in the design.