3/4” Return Lines causing changes in return pump flow?

[Cameron Smolinske]

On my 170 tank I have a 3/4” return line that splits and feeds 2 separate lock line returns into the tank. Ever since I’ve set this tank up I’ve noticed that I am constantly having to adjust my gate valve on my drain line because of fluctuating levels in the overflow box, which in turns causes a change in the level in my sump which causes issues with my ATO. Are the 3/4” lines the cause or could there be something wrong with my drain line? Return pump is a Sicce SDC 9.0 (older model) TIA for any help

 

[KrisReef]

When the drain flow is unstable, the level in the sump will reflect this. The most dramatic results from starting and stoppping of full siphon in one or more drain pipes. Getting all of these things balanced out can sometimes be a challenge, and in other set ups they just flow evenly on start up.

The return pump, if it is old, may contribute, but in general I would suspect that the drain is cycling between full siphon and siphon failing? Do your drains make noise, and does the noise change or cycle?

 

[Cameron Smolinske]

When the drain flow is unstable, the level in the sump will reflect this. The most dramatic results from starting and stoppping of full siphon in one or more drain pipes. Getting all of these things balanced out can sometimes be a challenge, and in other set ups they just flow evenly on start up.

The return pump, if it is old, may contribute, but in general I would suspect that the drain is cycling between full siphon and siphon failing? Do your drains make noise, and does the noise change or cycle?

Drain doesn't seem to go from full syphon to failing syphon. Pump is only about 6 months old but is the older style SDC with the elongated controller. Being that it was probably New Old Stock I am starting to wonder if that's the problem. However there is no noticeable cycle to it happening. I usually notice it if I am sitting near the tank and I hear the ATO running constantly.

Kind of at a loss at what to do that doesn't involve replacing the return pump and upgrading the return plumbing to mostly 1".

 

[mfinn]

If you can post pictures of the return lines, where they split and go to the tank.
Post pictures of the drains in the overflow box and under the tank. And gate valve.

 

[Cameron Smolinske]

 

[Freenow54]

All I can tell you is that mine is 2 pipe with a DC pump. The line coming from the Tank which is internal is 1 inch. The return to the tank is 3/4 . Never had an issue . Mine is split as well . No valves just control with the pump. 2 90s in the drain. @ from the sump up and over . 2 90s in the return line .Just a small vent hole in the drain , on a 90 which is inside the internal overflow. I had no choice and would never have a one pipe drain again

 

[mfinn]

The return plumbing size has nothing to do with the fluctuations on the sump and overflow box.

Can't see anything with the pictures.
I take it there are 2 drains.
One is a main drain with the gate valve on it and the other is an emergency drain?
Is there a pipe in the outside overflow box for the main drain?

How does the water get from the tank to the outside over flow box?

One observation right now, is if a few inches in the overflow box makes a difference in the sump making the ato to go on, you have too little water in the sump.

 

[Vivid Creative Aquatics Verified Sponsor]

I know it probably unlikely , but just t be rule it out - is the Sicce SDC 9.0 pump running in "constant flow" mode , or is it in one of the other flow modes?

Lagoon / Ripple: Fluctuates the flow output with gentle variations to mimic natural, rolling water movement.

Reef Crest: Simulates stronger, surging wave patterns and variable bursts of current.

Slow Current / Fast Current: Alternates between designated high and low flow parameters to change up circulation.

 

[Cameron Smolinske]

The return plumbing size has nothing to do with the fluctuations on the sump and overflow box.

Can't see anything with the pictures.
I take it there are 2 drains.
One is a main drain with the gate valve on it and the other is an emergency drain?
Is there a pipe in the outside overflow box for the main drain?

How does the water get from the tank to the outside over flow box?

One observation right now, is if a few inches in the overflow box makes a difference in the sump making the ato to go on, you have too little water in the sump.

I have three drains on with no standpipe and one that has a certain length standpipe and then an emergency standpipe. As I try to keep it adjusted to where the full siphon on the no stand pipe and the other two stand pipes are dry. Is it possible that I’m doing that wrong and the second drain with the shorter standpipe needs to be full siphon ?

 

[Jamie814]

I have three drains on with no standpipe and one that has a certain length standpipe and then an emergency standpipe. As I try to keep it adjusted to where the full siphon on the no stand pipe and the other two stand pipes are dry. Is it possible that I’m doing that wrong and the second drain with the shorter standpipe needs to be full siphon ?

The shortest standpipe (or bulkhead with no standpipe) should run as a full siphon controlled by a valve. The second standpipe should be set up like a Durso, allowing just a trickle of water where the fluctuation occurs. The emergency standpipe should remain dry unless the water level gets too high. You’ll never be able to perfectly match a full siphon to a return pump because there are too many variables, which is why the second standpipe handles the overflow and balances the drain flow.

 

[mfinn]

The shortest standpipe (or bulkhead with no standpipe) should run as a full siphon controlled by a valve. The second standpipe should be set up like a Durso, allowing just a trickle of water where the fluctuation occurs. The emergency standpipe should remain dry unless the water level gets too high. You’ll never be able to perfectly match a full siphon to a return pump because there are too many variables, which is why the second standpipe handles the overflow and balances the drain flow.

This is the way mine is set up.

 

[Vivid Creative Aquatics Verified Sponsor]

I have three drains on with no standpipe and one that has a certain length standpipe and then an emergency standpipe. As I try to keep it adjusted to where the full siphon on the no stand pipe and the other two stand pipes are dry. Is it possible that I’m doing that wrong and the second drain with the shorter standpipe needs to be full siphon ?

is it possible that the drain with now stand pipe (the fill-siphoned one) is intermittently creating a small vortex to the surface and drawing in air, thus breaking full siphone?

If you discover that to be the issue, it's simple fix.

add a U pipe (two 90deg elbows) to the open bulkhead that is your full-siphon. this would effectively make it so the opening faces downwards towards the floor of the overflow box and prevent it form forming a vortex and sucking in air