Water level in sump fluctuating

[zenzence]

Hey everyone,
Just moved my 90 and for some unknown reason the water level in my sump is fluctuating about 2 inches every 20 seconds or so. What causes this I am using a mega overflow and a mag 7 pump. What should I attempt to adjust to prevent this?

[Aquaduck]

Sounds like you have a problem with your overflow. It could be starting a siphon and sucking the water out of your overflow box. Once the siphon is broken it refills and repeats. This would make your sump level fluctuate every few seconds. Details of over flow drain would help.

[zenzence]

its a mega overflow box I have a mag 7 as a return pump. You are exactly right I can see it start sucking the water from the overflow into the sump. I just cant figure out how to stop this from happening.

[Aquaduck]

Perhaps you are trying to push too much water through the overflow system. Try restricting the pump outlet with a ball valve. Does your overflow pipe have provision for letting air in at the top? I don't recall what the Mega overflows look like.

[Afishianado]

You need to throttle the air intake at the overflow. Most people who use a Durso overflow have this exact problem, a simple throttle will balance this out and you won't have to reduce your return pump flow. You could do this with a valve, or you could do it by hand. Do a search for durso overflow and flushing, that is term that I seen most often applied to this situation.

[Aquaduck]

Go here for Durso information: DURSO STANDPIPE
There's also info on modifying a Mega overflow for more flow.

[zenzence]

Ok i have inserted a air line into the durso and still it flushes. I used a I.D. 1 inch drain pipe. Could this be the problem will increasing the diameter of the drain tube increase the flow preventing flushing?

[Aquaduck]

What size is your return line? My drain is 1.5" and uses a Durso with one hole drilled in the top to let air in.

[zenzence]

The inside diameter is 1 inch maybe this is my problem what do ya think

[Aquaduck]

Yes. Having the return line and the drain line the same size is the problem. You will need to change the Durso to use 1.5" pipe and then use a reducer to go through the bulkhead on the bottom of the tank. Then use an adapter on the underside of the tank to go back up to 1.5" to drain into the sump.

[Afishianado]

Just having an airline at the overflow drain may not be enough. Often people need to use a valve to adjust the air intake until they find the sweet spot where the air and water flow continously and at a balanced rate.

[zenzence]

ok I placed two airlines down the durso and it appears to be working nicely. One more thing is it ok for the drain pipe to be below the water surface. It is very loud if it isnt below the water line.

THanks for the help guys I really appriciate it

[Aquaduck]

If you mean the end that is in the sump, then yes it can be submerged and should be to reduce noise and splashing.

[zenzence]

hey thanks again I change the drain to 1 1/4 diameter and removed the air line and the overflow works like a charm.

[Aquaduck]

I'm glad it worked out for you.