help needed with plumbing - gurgling on returns

[davidm]

I?m having trouble with the returns on my new setup gurgling.  It is a 180 gal tank with two one inch holes in the back of the tank. The flow is via an Iwaki 70RLT which pumps about 1300 gph at this head of 10 feet.   I put a diagonal plexiglass wall running along the back of the tank so the water needs to flow over this wall to enter the holes in the back of the tank, which are about 2? from the top of the tank, and 1? below the plexiglass waterfall.  The waterfall works great and makes no sound.  I put a PVC T after the holes, and 1? flexible PVC runs down 10? to the sump. It looks something like this (looking down across the length of the tank)  |-  /  . The gurgling occurs at the T as the water begins to fall out of the T into the pipe.  If I block off the top of the T (making it into an elbow of sorts) the water level drops until air is sucked into the holes of the tank making another gurgling sound.  So how do I stop the suction and sucking of air into the return?  I tried lowering the flow (increasing resistance on the pump) but that only made the gurgling less frequent but just as loud.  Should I put resistance on the returns?

 

Thanks for any advice.  Plumbing is not my friend.

[Larry Grenier]

I'm having a hard time picturing your setup but see if this makes sense.  Put an airline down into your return with the other end above the tank thus making a constant air feed into the overflow kind of like the air feed on a durso overflow.  You might put an adjustment valve on the end in the air to see what effect varying the amount of air entering the airline has.

[michaelg]

I think you will solve it if you put a cap on the top of the T and drill a small hole in it.  Look at some of the modified durso-standpipe designs.  You are pretty close- only want a little air, not a lot.

[davidm]

sorry, i should have mentioned I put a cap on top of the T and drilled holes of various sizes with no success.  will try the tubing tonight, otherwise I may have to redo the entire drain system.

any other advice would be appreicated.

[Sph2sail]

I had a similar noisy problem with my Durso standpipe return.  I found that I had too much of a vertical run going down (almost 4.5 feet) and it overpowered the air relief in the Durso, causing it to cycle and gurgle and sound like a dog throwing up...  :p

 

The fix was to put a 90 degree elbow at the base of the standpipe (which is now about 24" drop) then use re-inforced clear pvc hose in a slow gentle arc back into my sump.

 

Lots of air flow/bubbles in the flow past the 90 degree, but no more cycling and gurgling.

 

steve

[michaelg]

David- any chance you can get a photo up?  I am having trouble picturing what is before the pipe.  Is it an elbow that the water enters into, or just a straight bulkhead?

[davidm]

I think my problem was compounded by the error the water was just entering into the flat bulkhead straight on (on the back top of the tank).  took it apart last night and put it an elbow facing down which seems to help.  will try re-building it tonight, if I can find the parts, following the original Durso specs more exactly - mainly making the  plumbing T and downspout > bulkhead, right now they are equal (1 inch).  wish me luck, i need to fix this yesterday.  thanks for all the advice, david

[michaelg]

That should do the trick.