Overflow and return pump not matching flow

[Timmybme]

I’m getting back into the hobby and am having a big issue.
I have a 758 GPH return pump and a 800 GPH hob overflow.
I have a three compartment sump with the return pump in the last compartment.
The issue is that the pump runs itself dry and is overmatching the overflow box.
I installed a ball valve on the return line as well as a check valve but I just can’t get the flow to even out.
What am I missing PLEASE?
Thank you in advance for any suggestions

 

[threebuoys]

I assume your return pump is not variable speed DC. So, your only choice is to partially close the ball valve. Just do it in very small increments and give the tank time to adjust. It can be a slow process to tune it in so the flows match.
Put a horizontal mark on your return chamber as a benchmark so you can determine if your adjustments are working. Then, going forward evaporation will cause the water level to drop in the return chamber and the mark will indicate the amount of fresh water you need to add to maintain salinity.

 

[redfishbluefish]

I've got a hunch you don't have enough water in your tank and your sump can't handle that extra volume. When you turn your return pump on, water has to flow into the DT until the sawteeth reach their flow limit. For me, that's about two gallons.

What size tank and what sump (or if DIY, is there extra volume in your sump. Remember, when your pump is off, the return section of the sump is going to be overfilled.

 

[Timmybme]

74 gallon tank, 20gallon sump
Is this adjusting period normal, like have you all run into this at all?

 

[Timmybme]

Sorry, 75 gallon...
I’ve added as much water as I can without overflowing the tank or sump.

 

[threebuoys]

My return pump is DC variable speed, so that gives me an option you don't have. When I said the tuning process was slow, I meant it might take you 30 minutes or so of minor adjustments to the return valve to let the water level out in the tank and in the sump. Your other option would be to add additional overflow plumbing to increase the amount flowing into the sump. Perhaps the height of the overflow plumbing in the tank is too high and doesn't allow enough water to enter?

 

[Hermie]

I’m getting back into the hobby and am having a big issue.
I have a 758 GPH return pump and a 800 GPH hob overflow.
I have a three compartment sump with the return pump in the last compartment.
The issue is that the pump runs itself dry and is overmatching the overflow box.
I installed a ball valve on the return line as well as a check valve but I just can’t get the flow to even out.
What am I missing PLEASE?
Thank you in advance for any suggestions

you probably aren't getting 800 GPH on the overflow unless it's fully siphoned, I could be wrong. But what you can do is plumb a line off your return and cycle it back into your sump. So it diverts flow and reduces the flow going to the display. Instead of the ball valve you can put a T; but a gate valve is better than a ball valve for controlling flow rates. Ball valve is very hard to dial in.

 

[mdb_talon]

As others said it sounds like too much pump for overflow(assuming sump is "full" with pump off.

Either divert part of it as mentioned or buy smaller return pump(preferably DC controllable). Also will add that yoy mentioned a ball valve on the drain side which is fine for times you may want to turn it off. Do not try to adjust flow with that though it should always be fully open.

 

[KStatefan]

There is nothing wrong with closing the valve done to reduce the flow to the tank

 

[Timmybme]

Thank you guys, I love the willingness to help out another fellow reefer.
I bought a higher capacity OF. It’s 1040 GPH.
It’s getting delivered tomorrow so we will see.
I will also look at adding water.
I may have been mistaken when I said earlier that I can’t put more water in.
Thanks again but keep the ideas coming.