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Ebb&Flow: Drainage rates - inlet VS outlet tubing size

I'm still in the process of designing my first system and have started to wonder about the size of my outlet tubing.  I plan to fill my beds from 1/2" pvc, but am not sure if I should make my drain outlets 3/4" or 1" pvc.

 

The bigger the tube, the faster it should drain.  But are there any negatives to using a larger diameter?  I'm going to make an auto-siphon out of a loop of flexible pvc....could tube size adversely affect siphoning ability?

 

Installing larger drain tubes in the beginning could make it easier to add new modules to the system later....

 

Anyone have any thoughts on this?  I noticed the barrel aquaponics systems drain from 1/2" pipe.

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If you are pumping into a bed with 1/2" pipe, that flow is going to be under some (though minimal) pressure and therefore  will deliver quite a bit more water than the same size pipe working as a gravity drain.

 

ALWAYS UP SIZE GRAVITY PLUMBING

 

For a combined drain, I would move up to 2-3" depending on how many how big the grow beds are but that is just me, I build big systems.  I suppose 1 1/2" pipe might work for a small run of combined drain.

 

If doing loop siphons, I would make sure the drain connections allow air at the bottom of your loops.  Like have the flexible tubing just stuck in uprights of say 1 1/2" or 2" pipe so that they will be able to suck air from both ends when the siphon should kick out.  If you seal up a combined drain, there will be a tendency for all siphons to kick when one does.

 

Now size of siphon needs to balance with flow rate and barrels cut the long ways can give some difficulty with siphons.  I would probably do 1" plumbing through the grow bed and then adapt to whatever is appropriate for a loop siphon that will work with the flow rate (perhaps 3/4".)

Exactly as TCLynx says. Always upsize gravity plumbing.

 

I am filling my growbed with 3/8 ID tubing, and am having trouble draining it with 1" ID tubing.

 

You will probably need to put in a bit of a restriction  (smaller tubing) somewhere around the auto-siphon to get it to start correctly, but after the auto-siphon go overly-large. It's easier to downsize the first 2 feet than it is to upsize the whole run to the tank/sump.


TCLynx said:

If you are pumping into a bed with 1/2" pipe, that flow is going to be under some (though minimal) pressure and therefore  will deliver quite a bit more water than the same size pipe working as a gravity drain.

 

ALWAYS UP SIZE GRAVITY PLUMBING

 

For a combined drain, I would move up to 2-3" depending on how many how big the grow beds are but that is just me, I build big systems.  I suppose 1 1/2" pipe might work for a small run of combined drain.

 

If doing loop siphons, I would make sure the drain connections allow air at the bottom of your loops.  Like have the flexible tubing just stuck in uprights of say 1 1/2" or 2" pipe so that they will be able to suck air from both ends when the siphon should kick out.  If you seal up a combined drain, there will be a tendency for all siphons to kick when one does.

 

Now size of siphon needs to balance with flow rate and barrels cut the long ways can give some difficulty with siphons.  I would probably do 1" plumbing through the grow bed and then adapt to whatever is appropriate for a loop siphon that will work with the flow rate (perhaps 3/4".)

thanks for the replies.

you can see that i'm already planning to 'upsize' my outflow (.5" in -> .75" or 1" out)....guess i'll go with the 1" for faster draining.  i can always downsize to smaller tubing if i need to slow down the cycle.

while learning and experimenting, its better to give myself more options for making adjustments.  ;)

exactly!

Averan Gale said:

thanks for the replies.

you can see that i'm already planning to 'upsize' my outflow (.5" in -> .75" or 1" out)....guess i'll go with the 1" for faster draining.  i can always downsize to smaller tubing if i need to slow down the cycle.

while learning and experimenting, its better to give myself more options for making adjustments.  ;)

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