Tank randomly fills to the top

blackflme · Jan 11, 2017

Hey everyone, I'm hoping someone can help me out with a new problem I have been having. I have a 29g tank with a sump using a hang on the back overflow. I've had this setup for over a year now with no problems until recently.

This has only happened twice so far. Out of no where without touching the system for days(aside from adjusting skimmer level) the tank level rises to the very top of the lid. As close as you can possibly get to overflowing. The thing that boggles me is that it never overflows. The water level just stops rising. So after coming home from work I walk inside to hearing my skimmer screaming because the sump pumped too much water into the tank and the skimmer wasn't submerged.

The first time the siphon seemed to be not so great and the sump water level was a bit low. So I restarted the siphon, added water, and it was fine. The next time the water level in the sump was fine, the siphon seemed ok, and just restarted the siphon and it all seems to be fine.

Any advice on why this is happening? I really don't want to keep blowing through skimmers lol.

Nick92515 · Jan 11, 2017

What type of overflow system are you running. Is there anything blocking the drains or the weir?

blackflme · Jan 11, 2017

What kind of details are you looking for? I just know its a gravity/siphon hang on the back overflow. I can't remember the size of the return pump or the overflow, but they have been working great together for over a year.

I will check for any blockage. I just looked at the filter in the overflow and that looks like it could use a cleaning.

happyhourhero · Jan 11, 2017

If you have the prefilter sponge or anything that could possible restrict flow, I would remove it.

blackflme · Jan 11, 2017

ok, I'll try that. Has anyone ever had this type of thing happen?

Bradw18 · Jan 11, 2017

Pics of set up

reef lover · Jan 11, 2017

Might not b anything to do with it. But make sure the u tube is clean. I find that as algae and debris get stuck to the inside the slower the siphon is.

Water Dog · Jan 11, 2017

It's definitely the pre-filter sponge clogging. When I had an HOB overflow on my 29 gallon back in the day, the same thing happened to me too. I ended up getting rid of the sponge. That led to a massive gurgling noise which was remedied by putting in a stockman standpipe over the drain. Worked very well.

happyhourhero · Jan 11, 2017

I have my return pump in a chamber that will run dry before my tank overfills and I have my return box high enough that if the return fails, not enough water can get into the sump to flood it either. I also have a black line drawn on my overflow outside of the tank so at a glance I can make sure my water is below that line. Of all things to stay on top of, overflow maintenance is up there.