Rising water in DT

gaz · Jul 26, 2017

Hi everyone, I'm having issues with the water level rising in my DT, here's some pics of my overflow

I have tried ramping my DCS2000 pump right down (only on 3 lights)but the water level still slowly rises in my DT but not at the back of the overflow.
Any help would be much appreciated

143MPCo · Jul 26, 2017

IMO, you have a siphon break (accumulation) in your overflow, air is getting in and causing the unit to lose suction. You can see that happening from the air pocket in the upper part of the overflow. You can add something like a lift (Tom'Aquatic) pump to continuously remove the trapped air and keep the siphon working optimally.

chipmunkofdoom2 · Jul 26, 2017

I have an overflow box and this happens when my U-tube begins to grow algae. I am running my overflow box close to its maximum capacity, so whenever algae begins to grow in the U-tube, this slows down flow just enough that the water level goes up in my DT, and goes down in my sump. Once I take a bottle brush to the U-tube, the levels go back to normal.

It looks like your overflow box has a weir, so it might be harder to determine this. Do you know how much flow you're returning to the tank and what your overflow's maximum rating is?

gaz · Jul 26, 2017

Not to sure on the maximum rating,the guy I brought it from said the 2000gph pump would work the best on this overflow box. I've drilled the hole bigger on the top of the durso and put some air hose in with a RO tap fitted so I could adjust airflow(see pic one). I cut the airflow off a bit and the water level in the tank instantly went down but I can see the water level slowly rising again.

143MPCo · Jul 26, 2017

gaz said:
Not to sure on the maximum rating,the guy I brought it from said the 2000gph pump would work the best on this overflow box. I've drilled the hole bigger on the top of the durso and put some air hose in with a RO tap fitted so I could adjust airflow(see pic one). I cut the airflow off a bit and the water level in the tank instantly went down but I can see the water level slowly rising again.

You will keep having this issue, as the water falls over the teeth of the overflow it pulls in bubbles, some of them break and that's the end of them, others get sucked in and create that air-pocket seen in your first picture, growing over time and reducing the flow of water. Unless you take permanent steps to remove the air you WILL continue to have water level rising in my DT.

gaz · Jul 26, 2017

Ok so do I just connect that lift pump up to where the air-syphon hose sticks out?

143MPCo · Jul 26, 2017

gaz said:
Ok so do I just connect that lift pump up to where the air-syphon hose sticks out?

That would be my recommendation, yes.

chipmunkofdoom2 · Jul 26, 2017

143MPCo said:
You will keep having this issue, as the water falls over the teeth of the overflow it pulls in bubbles, some of them break and that's the end of them, others get sucked in and create that air-pocket seen in your first picture, growing over time and reducing the flow of water. Unless you take permanent steps to remove the air you WILL continue to have water level rising in my DT.

This is not necessarily the case. I've had several tanks with external overflows. The only ones that have an issue with bubbles forming in the U-tube are ones that were vastly oversized. Because the flow through the tube was so slow, as you mentioned bubbles built up. Over time, the air would build up and the siphon would break. My overflow on my current tank, however, is much better sized. The flow going through it is so brisk that no bubbles accumulate. I've never once had to restart the siphon, or even ever seen bubbles resting in the tube for that matter.

gaz · Jul 26, 2017

I don't have to restart a siphon after I've turned the pumps off it just starts back up by itself. I'm at a loss at the moment, just thinking about taking the system down and starting again. Would the pump not draw water out of the overflow? Any other ideas on what I can do?

143MPCo · Jul 26, 2017

chipmunkofdoom2 said:
This is not necessarily the case. I've had several tanks with external overflows. The only ones that have an issue with bubbles forming in the U-tube are ones that were vastly oversized. Because the flow through the tube was so slow, as you mentioned bubbles built up. Over time, the air would build up and the siphon would break. My overflow on my current tank, however, is much better sized. The flow going through it is so brisk that no bubbles accumulate. I've never once had to restart the siphon, or even ever seen bubbles resting in the tube for that matter.

I don't beleave I said it was the case with ALL external overflows, my comments are specific to the OPs situation. As flow through an overflow is specifically relative to the amount being produced by a return pump, the downstream pipe is a factor, if not correctly sized for the flow it will limit the amount of water you can get through it, but it's the relationship between the amount of water being pumped by your return pump that dictates the optimum size that the overflow should be rated for in order to maintain proper flow through it.

I do agree with you however that faster moving overflow will "minimize" the amount of microbubbles trapped at the top of a U-shaped drain. However, it does happen from time to time I've seen it myself on 3 tanks that I have owned. In any case if the siphon breaks due to microbubbles being trapped in either a U-shaped drain or a J-frame drain as the OP has in this instance, it will cause flow restriction at the overflow, and as the return pump is still pumping the same amount of water, you will get a rise in display tank water levels.

Edited: An accumulation not siphon breaks*