Overflow problems

[The Guy]

Originally Posted by reefwars

Also if your valves are at tank level then tuning it is going to be harder then if the gate valve was at sump level.


In order to get a precise level height in your overflow box that doesn't fluctuate you need a stable return section and proper plumbing design and materials .

Agreed, I would leave the ball valve wide open and add a gate valve down at your sump.

[eli@fijireefrock.com]

Agree with the above.
The water level fluctuation in your sump will play a big role on the pressure of your return pump giving you different water levels in your overflow box and it seems you let the water drop too low in your sump before replenishing the evaporated water.
By now if your sump is one compartment best is getting a ATO and a gate valve is best.
Or if you have different compartments in your sump and your return pump is in one try never to get the water level in the sump go over the compartment separation level for the return pump as this will void its job of keeping the main tank water level in check.

[intarsiabox]

What kind of plumbing design did they put in your overflow box? Is there not an emergency drain line? I'm guessing it's a herbie style if there is a valve on the overflow drain line to the sump.