Return line: how big should it be?

[Dan Ponton]

I am having a problem with the bell siphons. I have a 2" pvs return line that is gravity feeding back to the fish tank. Some of the bells are working fine, but some are breaking to soon and only drain about halfway down.

I am thinking the back pressure created from the 2" line filling with water is causing them to break to soon.I will have about 10 half barrels draining into this line when all is done.

Also there is only about 2-3" drop on the line.

Should this be a 3" line?

Or I can also add a sump next to the pool and U siphon which will add some drop to the return.

[TCLynx]

Using food can bring cats and chickens, however trying to herd them into a container is often not possible even with food.  Ducks are far easier to herd.

[Tony Gilliam]

TCLynx, I'll give you that, It is hard to herd cats.

You wouldn't happen to know the max flow rates for pvc pipe?

[David]

My kat herds the hoomans. Any sudden moves are met with flawless fatalities.

[Dan Ponton]

I found this, hope it helps. Based on the below numbers in green, a 2" pipe should be more then enough.

I added a 2" vend pipe, found some of my bell caps were leaking air and I think that fixed the problem.

			Assume Gravity to Low Pressure. About 6f/s flow velocity, also suction side of pump		Assume Average Pressure. (20-100PSI) About 12f/s flow velocity		Assume "High Pressure" PEAK flow. About 18f/s flow velocity*
Sch 40 Pipe Size	ID (range)	OD	GPM (with minimal pressure loss & noise)	GPH (with minimal pressure loss & noise)	GPM (with minimal pressure loss & noise)	GPH (with minimal pressure loss & noise)	GPM (with significant pressure loss & noise)	GPH (with significant pressure loss & noise)
1/2"	.50-.60"	.85"	7 gpm	420 gph	14 gpm	840 gph	21 gpm	1,260 gph
3/4"	.75-.85"	1.06"	11 gpm	660 gph	23 gpm	1,410 gph	36 gpm	2,160 gph
1"	1.00-1.03"	1.33"	16 gpm	960 gph	37 gpm	2,220 gph	58 gpm	3,510 gph
1.25"	1.25-1.36"	1.67"	25 gpm	1,500 gph	62 gpm	3,750 gph	100 gpm	5,940 gph
1.5"	1.50-1.60"	1.90"	35 gpm	2100 gph	81 gpm	4,830 gph	126 gpm	7,560 gph
2"	1.95-2.05"	2.38"	55 gpm	3300 gph	127 gpm	7,650 gph	200 gpm	12,000 gph
2.5"	2.35-2.45"	2.89"	80 gpm	4800 gph	190 gpm	11,400 gph	300 gpm	17,550 gph
3"	2.90-3.05"	3.50"	140 gpm	8400 gph	273 gpm	16,350 gph	425 gpm	25,650 gph
4"	3.85-3.95"	4.50"	240 gpm	14,400 gph	480 gpm	28,800 gph	700 gpm	42,000 gph
5"	4.95-5.05"	5.563"	380 gpm	22,800 gph	750 gpm	45,000 gph	1100 gpm	66,000 gph
6"	5.85-5.95"	6.61"	550 gpm	33,000 gph	1100 gpm	66,000 gph	1700 gpm	102,000 gph
8"	7.96"	8.625"	950 gpm	57,000 gph	1900 gpm	114,000 gph	2800 gpm	168,000 gph

[David]

Good deal Don,

Did you glue them or use sealant?  I use plumbers tape on most fittings now but Im glad you got it resolved. 

-David

[Calvin Wyatt Rodriguez]

I just build a grow bed 3'x 8' 12" deep with a 1" fill and a 2" drain bell siphon. The bed never drains more than 1/2 way down (gravel screen is an 8" pvc pipe with slits cut in on an angle by a 1/8 skil saw blade all about 3/16 apart, abundant flow) (I plan to downgrade the drain stand-pipe to 1 1/4" from the current 2" to slow flow rate thus allow more drainage before siphon break) which leads me to my question.... How can I determine if I have an anaerobic zone in a grow bed due to improper drainage?

[David]

You will smell it.

Calvin Wyatt Rodriguez said:

I just build a grow bed 3'x 8' 12" deep with a 1" fill and a 2" drain bell siphon. The bed never drains more than 1/2 way down (gravel screen is an 8" pvc pipe with slits cut in on an angle by a 1/8 skil saw blade all about 3/16 apart, abundant flow) (I plan to downgrade the drain stand-pipe to 1 1/4" from the current 2" to slow flow rate thus allow more drainage before siphon break) which leads me to my question.... How can I determine if I have an anaerobic zone in a grow bed due to improper drainage?

[Calvin Wyatt Rodriguez]

TY

[Tony Gilliam]

I'm thinking worms wont live in the anaerobic zone.