Anti-siphon Hole for return

dirtj

New Member
My return elbow goes under the waterlevel in my main tank. It goes to far down in to my display thus causing a small flood from my refugium when the power goes out.
This is a DIY set-up, and I have heard of a hole being drilled somewhere in the vicinity of the return line @ where it goes over the tank into the display.
If the hole was drilled outside of the water, wouldn't water shoot out when the power is on?
Any help is appreciated.
Thanks alot!
 

johnnysalt

Member
yep.
so you drill it just under the water line. BEFORE you drill it though, do a recreation of the power outage: before your refugium fills up, look on the return plumbing to see where you need to drill it.
hth,
John
 

robchuck

Active Member
I once had the same problem and decided to drill holes in my returns to stop the floods. I used a 3/8" drill bit and drilled one hole on each of my return lines about 1/2" below the surface of the water. Some water escapes from the holes during normal operation, but it helps to keep the surface agitated.
 

bang guy

Moderator
Mine are drilled just barely below the waterline. I drilled them at an "up" angle so that water shoots down at a 45 degree angle. This keeps the hole open.
 

dirtj

New Member
I could be mistaken, but I believe I have seen these holes drilled above the water line, like at where the return line "ells" over into the tank. would this work?
 

bang guy

Moderator
I would worry about salt creep from spalshing water. Other than that it will certainly work that way.
 

robn

Member
I'm still a little confused about this, so please hear me out.....
I have a HOB overflow and PVC coming back from the sump into the display tank......the PVC is under the display tank water level (actually I have a wand over the water level right now, but I'm doing to change that this weekend, too much salt creep from the spray and too much microbubbles)........say that there is no anti-siphon hole in the return.....the lowest that the display tank will drain down to is to the overflow box level , right? OK, say I DO have an anti-siphon hole just under the normal display tank water level....even if the water level drops to below the anti-siphon hole, it should still keep draining out the overflow box....so it's still going to drop to the level of the overflow box......isn't it???:notsure: So, isn't the sump level maximum this: (normal display level - overflow box level) + current level in sump ?????
Also, aren't we talking about a return pump failure anyway? And if so, I don't see what difference the anti-siphon hole would make...if the pump quits, the water in the return pipe should drop back down into the sump....
Oh, my aching head
:help:
 

bang guy

Moderator
Not necessarily pump failure, a power outage will do the same thing.
If your return nossle is 4" below the water surface then without an anti-siphon hole the return line will drain 4" of water out of your tank. Most sumps don't have that much capacity and will overflow.
Just test yours out. unplug your pump and see what happens.
 

robn

Member
Yeah, I see what you're saying.....I replaced my spray bar tonight... left the tee in there but just have 2 outputs about 2" into the water.......I forgot to drill the siphon holes but it should be easy to go back and redo.....
I understand what you are saying....thanks!!!!
 

oscardeuce

Active Member
How about adding a one way valve to the system as a back up? this worked for me when my AS hole plugged with salt.
 

johnnysalt

Member
oscardeuce:
your as-hole? ...plugged with salt?
nobody wants to hear that, man. sounds like you need to see a doctor too.
(Heh heh :hilarious just kidding!)
 
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