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How much water will pass through 50mm pipe at a given head?
http://byap.backyardmagazines.com/forum/viewtopic.php?f=8&t=20142		 Page 1 of 1
Author:  Marc d W [ Jan 4th, '14, 20:26 ]
Post subject:  How much water will pass through 50mm pipe at a given head?
I'm just getting to the point of installing my new tank, growbed and Barrels see http://www.backyardaquaponics.com/forum/viewtopic.php?f=1&t=16454#p389865 for the final expansion. I was intending to use a 50mm pipe to join the two tanks together to deal with any differences in the amount of water retuning to each bed. However, I found this season that tomatoes grow awesomely well in blue barrels but even with a 15 min on off cycle (F&D) the plants wilted during the day and really wilted on the hot days. So I have been running constant flood during the day. So all's good except that in my proposed plan the 50mm pipe will need to deal with 6000 to 8000 litres per hr being returned to the one tank that will need to make its way back to the other tank through the 50mm pipe.

My question is; at a given head of say 300mm, how much water will pass unassisted through a 50mm pipe per minute ignoring any friction losses?
Author:  Domani [ Jan 5th, '14, 00:38 ]
Post subject:  Re: How much water will pass through 50mm pipe at a given he
Marc, look here http://www.engineeringtoolbox.com/minor ... d_626.html to calculate it yourself. Good luck!
Author:  Yavimaya [ Jan 5th, '14, 05:58 ]
Post subject:  Re: How much water will pass through 50mm pipe at a given he
lol domani thinks everyone is a maths wizz. :laugh:

pity that wasnt an "input your values" calculator, would be quite handy if it was.

I cant actually help sorry marc, but i run 50mm back from my NFT to tanks, i have recently added another line running to there to open the pump up a bit more (i run 8kl/hr or a little under).
The drain used to cope ok before (running with one line - maybe 6-7kl/hr), but since i bumped it up the pump is too much for it, there is only 100mm head max.

It would seem that with open pipes and little head, 50mm can handle atleast 5kl/hr, but not 8kl/hr.- this is running mostly flat (only where it come off the roof has a large drop)
hope that helps give you an idea.
Author:  Domani [ Jan 5th, '14, 09:17 ]
Post subject:  Re: How much water will pass through 50mm pipe at a given he
Well, if I would ever have thought such a thing, you just made clear there is at least one exception, Yavimaya. :shock:
Author:  Domani [ Jan 5th, '14, 15:21 ]
Post subject:  Re: How much water will pass through 50mm pipe at a given he
Actually, there is a more comprehensive way to calculate it - http://www.engineeringtoolbox.com/darcy ... d_646.html. All nicely explained, just follow the links for individual terms as head loss, friction coefficient, Reynolds number etc.

Hope that helps!
Author:  Sleepe [ Jan 5th, '14, 19:22 ]
Post subject:  Re: How much water will pass through 50mm pipe at a given he
Domani wrote:
Well, if I would ever have thought such a thing, you just made clear there is at least one exception, Yavimaya. :shock:


Make that two Paul. :)

Marc why don't you do the balancing act with valves with the 2" as a safety measure and I would be worried about the tom's wilting on a 15/15 F&D even in our heat. :drunken:
Author:  Domani [ Jan 5th, '14, 19:35 ]
Post subject:  Re: How much water will pass through 50mm pipe at a given he
Allright then!

Assuming your tanks are positioned right next to each other with not more than 1 meter distance from tank wall to tank wall, a 50mm diameter PVC pipe (that is, the inside diameter) can handle nearly 12.500 LPH (3,300 GPH) at a head of 300mm. That is while ignoring any friction losses.

Add a T branch on top of a SLO in one tank and it will reduce to only 3.000 LPH (795 GPH). Which illustrates what such a T fitting can do to your flow. Ball valves can also cause some nice extra friction losses on such short distances. Calculations are based upon the Hazen-Williams formula.

Hope this answered the question.
Author:  Marc d W [ Jan 5th, '14, 22:31 ]
Post subject:  Re: How much water will pass through 50mm pipe at a given he
thanks Yavimaya. I did see Paul's post at 1 am this morning and went whoa :shock: . lots of useful info but a bit out of my league :think: particularly at that time of the morning :?
Anyhow I have been out all day and not been able to follow the thread so it has been good to see some more info while I have been away.

so if I follow you Yavi, you are saying that at about 100mm head a 50mm pipe handles about 6kl an hour in your system? :cheers:

Paul you're a champ for doing the maths for me :cheers: :notworthy: . So it seems that the 50mm pipe joining the 2 tanks will do the job. The gap will be less than 300mm so I will probably use a slip fitting. As I only need to deal with a max of 8000l per hr and I will probably join them 400mm down`I should have plenty of leeway.
Could you please post how you worked it out so we can have a bash at trying to do it for ourselves.

one of my mates suggested the Diameter Velocity & Flow Rate Ultra Calculator at http://www.1728.org/flowrate.htm but that stumped me as well as i only know the pipe diameter and not the velocity or flow rate.

Sleepe wrote:
Marc why don't you do the balancing act with valves with the 2" as a safety measure and I would be worried about the tom's wilting on a 15/15 F&D even in our heat. :drunken:


I'm not sure what you mean Sleepe re balancing them with valves.
Author:  Domani [ Jan 6th, '14, 00:11 ]
Post subject:  Re: How much water will pass through 50mm pipe at a given he
Marc, you can work it out with the Hazen-Williams formula (equations) or with the Darcy-Weisbach equation. The last one is commonly used by civil- and hydraulic engineers to calculate losses in pipe lines and predict flow rates etc.

I'm not an engineer and it costed me a heap of time to get it all together in a spreadsheet, for which I luckily could reach back to my extensive knowledge and experience in that field. Neither a qualified engineer or me will give away the painstakingly acquired knowledge on a silver platter (which reminds me of someone on this forum who lived with the believe that some of us were born with a silver spoon in the mouth and only for that we should share the spoon with him for free! :) ). So, that's propriety info.

If you really want to work out these calculations yourself, follow the links I've given before and you have all you need to get it done. Just put some sweat in it and it will be all yours and for free!
Author:  Sleepe [ Jan 6th, '14, 07:51 ]
Post subject:  Re: How much water will pass through 50mm pipe at a given he
Remind me not to post after getting in from work and having a few beers. :)

Taking this in stages
Why are the tom's wilting? young, too much foliage to root development? If 1 temporary shading if 2 pruning and checking root development. ? high nitrates without balancing P and K.

I am assuming you are going with the pump in each FT, is it possible to balance the return water with valves so that partial water goes to either of the FT's that needs to be balanced. This only leaves the 50mm to cope with minor variations.

Just thinking aloud. :)
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