Flirting With Disaster?

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Willz

Feeder Fish
MFK Member
Feb 9, 2011
177
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Roanoke VA
So, I built two of the 2nd type of DIY overflow (the non-skimmer type) out of 1.25" PVC. I set it up and started running it and realized that the pump was too much for the overflows to handle. Here is a pic of the type of overflow I built:

overflow.jpg


OK, not the best picture, but you get what I made. After getting carpet wet I went out and bought a ball valve to regulate the return line so that the pump wouldn't out pace the overflows. Then I also bought a T and put it ahead of the ball valve so the extra flow could go back to sump (pulled the impeller on a Magnum 350 and run it back through it for extra mech).

Here is a picture of the sump and return:

DSC00200.JPG


I made the overflows from a design here that said to not glue the PVC elbow to help prime it by turning it up. But I did seal the last elbow and it is in the water... So, now what seems to be happening is the water gets to the level of the elbow, then somehow starts sucking water in through the elbow until it drains to the level of the elbow and breaks suction. Then the tank's water level goes up until it starts sucking through the elbow. So the water level goes up and down. Pictures:

DSC00198.JPG


DSC00197.JPG


I am wondering if this is dangerous? Everything I have read suggests that the water level in the tank should be stable, the sump should fluctuate as the water evaporates, but that's it. This is making me nervous every day that I go to work. Does anyone have any ideas on how to fix this or if it's really dangerous, or am I just paranoid? I have diverted enough water that it doesn't overflow the tank anymore, but I still am nervous since it doesn't seem stable. Thanks in advance,
will
 
Here is a picture of the overflows before I installed them:

DSC00183.JPG


See how the 2nd elbow (above the T) is hanging in the tank? The water running back to sump creates a siphon there and pulls extra water from that elbow. Do I need to drill a hole in the top of that elbow to break the siphon, or is this safe?
 
My overflow is very similar except it does not siphon because the tank is drilled.
If I understand correctly I believe the problem is that when the siphon occurs it is suctioning too much for the pump and then once the level drops the siphon breaks and the water level rises till your siphon starts again.

Maybe I'm way off here but if you added a valve inline to the sump you could slow the siphon down to equal the return of the pump?

How strong is your pump (gph) and how large is the tank?
 
chris_zx2;4941906; said:
My overflow is very similar except it does not siphon because the tank is drilled.
If I understand correctly I believe the problem is that when the siphon occurs it is suctioning too much for the pump and then once the level drops the siphon breaks and the water level rises till your siphon starts again.

Maybe I'm way off here but if you added a valve inline to the sump you could slow the siphon down to equal the return of the pump?

How strong is your pump (gph) and how large is the tank?
Click to expand...

The tank is a 120 gallon and the pump is 1200 GPH (but with about a 4' head is probably closer to 900-1000). I also divert about 200 GPH back to the sump so the aquarium won't overflow. The sump itself is a 40 gallon breeder, but realistically holds about 15 gallons, so it won't overflow if the power goes out. The overflows aren't handling enough now, so I am scared to restrict them with a ball valve going back to sump. According to the sticky they both should handle 500 GPH, so I'm wondering why they don't handle the lower pressure.
 
You don't need the second U from the T going back into the tank that one needs to breath...You have your water level set with the T for heidth.... I see your using the U for support for the Overflow.....Yes if you drill a hole in the top of the U piece connected to the T it will not suck more water out of your tank.....
 
This will eliminate your water pulling through the pvc when electricity is shut off ... And you will not loose your siphon when the electricity shuts off.......It will only drain down to the T outlet you have set for heidth... then stop...
 
your pump is pumping faster than your overflow so the water level rises and the second U connected to the T siphons also....... maybe you need more holes in the inlet tube and you need to adjust with ball valve on your pump to slow it down to equal the Overflow..I had to build two overflow before I came up with the one I liked....
 
Thanks everyone! I wondered if I needed more holes in the inlet tube, and will drill a hole above the T on the "to sump" side of the plumbing to break the siphon on that side of it. I already have a T diverting some water back to sump, but will spend the afternoon trying to balance it after I have made the suggested mods. This article:
http://www.aquariumlife.net/print/article.asp?id=120
Is the one I based the design on, but I screwed up and got happy with the PVC cement and glued the one that is only supposed to slip on. I think that is the only difference between the one I built and the article. So, hopefully by the end of the day I will have done the work and have it balanced so the tank level doesn't fluctuate and I can leave for work tomorrow morning with no more than the normal level of Monday morning dread (haha). Thanks all!!!
will
 
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