Closed Loop Back Siphon Question...

SkinnyPete · 09/23/2007, 10:37 AM

I'm just setting up a 125g tank with drilled hole near the bottom of the tank. If I plumb a closed loop through this hole and run pvc as the return under the sand, there is no need to worry about back siphoning during power outages, correct? The pump can sit under the tank and there is no need to break siphon during power outage because the water has nowhere to go? Is there a need to worry about the pump leaking at all?

This is my first closed loop and I'm just nervous about the hole being about 4" from the bottom of the tank, and the pump under the tank. Seems like back siphoning wouldn't be a problem but, that's a lot of water so - just asking in case I'm missing something stupid.

Thanks.

AZDesertRat · 09/23/2007, 10:42 AM

A closed loop is just that, a closed circuit. There is nowhere for water to siphon to unless you disconnect the pump. You take water out of the tank, through a pump and back to the tank without ever exposing it to air or a sump.
I am not quite sure I understand the way you want to plumb it but I would return it close to the surface for surface agitation and oxygen exchange. My loop comes out of a drilled hole in the exact back center of the tank about half way down, goes through an OR 3500 pump then back up through a Ocean Motions Squirt two way into two drilled holes in the top back corners with 3/4" LocLine so I can move them around. There are ball valves at each bulkhead so I can remove the pump for cleaning and not flood things.

SkinnyPete · 09/23/2007, 11:03 AM

Thanks. Well, I just bought a used tank with dual overflows and one drilled hole very close to the bottom of the tank. I guess I could use that as the intake and return it at the top. But, I was thinking of using that hole to return by plumbing a series of outlets under the rock work.

I am going to have two returns from my sump at the top of the water, but as far as the closed loop goes...I only have one hole near the bottom to work with. Seemed like the obvious thing to do - use it to return under rock work. I'm open to ideas though.

AZDesertRat · 09/23/2007, 11:13 AM

I would run both overflows to the sump myself.
Use the hole close to the bottom for the closed loop suction and run your returns up and over the back corners with 90 degree elbows and some Loc Line.
Lets see what other people say.

09/23/2007, 10:37 AM	#1
SkinnyPete Registered Member Join Date: May 2006 Location: MA Posts: 95	Closed Loop Back Siphon Question... I'm just setting up a 125g tank with drilled hole near the bottom of the tank. If I plumb a closed loop through this hole and run pvc as the return under the sand, there is no need to worry about back siphoning during power outages, correct? The pump can sit under the tank and there is no need to break siphon during power outage because the water has nowhere to go? Is there a need to worry about the pump leaking at all? This is my first closed loop and I'm just nervous about the hole being about 4" from the bottom of the tank, and the pump under the tank. Seems like back siphoning wouldn't be a problem but, that's a lot of water so - just asking in case I'm missing something stupid. Thanks.

09/23/2007, 10:42 AM	#2
AZDesertRat Moved On Join Date: Jan 2002 Location: NW Phoenix Posts: 16,621	A closed loop is just that, a closed circuit. There is nowhere for water to siphon to unless you disconnect the pump. You take water out of the tank, through a pump and back to the tank without ever exposing it to air or a sump. I am not quite sure I understand the way you want to plumb it but I would return it close to the surface for surface agitation and oxygen exchange. My loop comes out of a drilled hole in the exact back center of the tank about half way down, goes through an OR 3500 pump then back up through a Ocean Motions Squirt two way into two drilled holes in the top back corners with 3/4" LocLine so I can move them around. There are ball valves at each bulkhead so I can remove the pump for cleaning and not flood things.

09/23/2007, 11:03 AM	#3
SkinnyPete Registered Member Join Date: May 2006 Location: MA Posts: 95	Thanks. Well, I just bought a used tank with dual overflows and one drilled hole very close to the bottom of the tank. I guess I could use that as the intake and return it at the top. But, I was thinking of using that hole to return by plumbing a series of outlets under the rock work. I am going to have two returns from my sump at the top of the water, but as far as the closed loop goes...I only have one hole near the bottom to work with. Seemed like the obvious thing to do - use it to return under rock work. I'm open to ideas though.

09/23/2007, 11:13 AM	#4
AZDesertRat Moved On Join Date: Jan 2002 Location: NW Phoenix Posts: 16,621	I would run both overflows to the sump myself. Use the hole close to the bottom for the closed loop suction and run your returns up and over the back corners with 90 degree elbows and some Loc Line. Lets see what other people say.