Adjusting Durso Overflow?

Hi All, Last weekend I installed 2 Durso overflows in my 120. I initially drilled the caps with a 3/16 hole in each, which turned out to be insufficient, so I added another hole to each. This seemed to do the trick, with the level holding about an inch above the intake (street) elbow. Today, however, for some reason the level started surging up and down, gulping air. I've made sure the air holes are clear with a toothpick, but this doesn't solve the problem. Anybody know how to fine tune these? TIA

Here's his email - try asking him direct.

Please let us know how you fix this! <G>

I think you have too much air now...or the level in the tank has changed since you made the 2nd hole (i.e. the return pump is fluctuating it's GPH, which the Durso cannot adjust to fast enough). Try putting a piece of tape over one of the holes and see if it calms down. If so, use a push pin tack and make a hole in the tape. you may need just a little more air, but not a 3/16 hole's worth.

HTH LT

Instead of drilling holes in the top of the cap, use a reducing bushing with a small valve like a 1/4' labcock valve. This way, one can control and adjust the amount of airflow. For mine, which are 2' drains - I use another elbow coming out of the reducing bushing with a 1/2' ball valve - works very well.

HTH,

Found the problem. I had installed a new sump and new skimmer. With the subsequent repiping, I had a sponge over the main pump intake. It had plugged with debris and was causing the return flow to surge. Off came the sponge and everything settled out nicely. Good call on the return fluctuation. Thanks All.

I prefer the drill method.. once it's done all you gotta do is clean the hole.. But for others..a suggestion would be to use a drip irrigation system spray head.. they have little needle valves and are all plastic.. Should cost about $1 I never tried it.. if someone tries it let me know how it works

I've seen a few posts in the past that suggest that the air hole is not necessary, and I think I agree. Nothing scientific behind that statement, just experience. I had trouble with mine and closed it up and put a ball valve on the drain line, and that stopped my problems. I use the ball valve to control the flow, with the same results. I think you're accomplishing the same thing by using the valve, and it's not problematic like the air hole. Royce

One thing I've recently found (that might possibly be) useful is to make the hole in the endcap 1/4' and then use a use a piece of 1/4' acrylic rod (length is something that needs a bit of experimentation but I'd say start with something approximating the length of your standpipe) and jam it into the hole and work it down into the middle/lower regions of the standpipe. (the inside diameter of the rod I'm using is about 1/8' BTW).

My theory on this is that by lowering the point where the air enters the downflow, the less chance you have of the water 'merging' again at the bottom and helps prevent that nasty slurp & gurgle we all hate.

I find that you can adjust the rod up and down and the water level in the overflow will respond accordingly. I haven't found any need to re- strict further restrict the air intake. I would assume that this may have something to do with atmospheric pressure (???)

If your valve gets clogged or even partially blocked you will have BIG problems.

A valve on the return line is a bad idea IMO. Why not use a valve on the air hole instead?

Well, I'm considering doing what the Royce said, but am also worried by your statement.

I'm having similar adjustment problems with my durso. I can get it adjusted so I get no noise from the overflow, but I get a lot of air bubbles in the sump, and noise from that. That's why I'm considering slowing the flow to the sump.

Is there an alternate way to lessen the ammount of air that gets to the sump?

hhmmm.. Seems I'm the only person that's never had any trouble with a durso.. they're bullet proof if keep the hole small and make it a siphon rather than a drain..To lessen bubbles, make it quieter and increase flow.. the outlet should be below the water level in your sump

And the only trouble with an air valve is that it'll clog then lower the overflow water level. Then it'll break siphon gurgle and dump bubbles in your sump