sump flow

[FAHADREEF]

i made this diy pipe overflow from youtube from the diy king on youtube and its working perfectly well problem is my sumps water keeps decreasing slowy, my return pump pumps 600 liters per hour and i dont tbh if i should make a thicker pipe overflow or buy a small return pump, but what's confusing me is somtimes it works perfectly and returns exactly whats going in but on the other hand it somtimes like now its taking water from my sump more then whats going it
if someone know or have in countered that problem before please tell me
thankyou

 

[T-J]

What size is the pipe?
I'm guessing it keeps fluctuating due to the pipe starting/stopping a full siphon.
You may need to go with a bigger pipe and a gate valve to dial it in.

 

[theMeat]

i made this diy pipe overflow from youtube from the diy king on youtube and its working perfectly well problem is my sumps water keeps decreasing slowy, my return pump pumps 600 liters per hour and i dont tbh if i should make a thicker pipe overflow or buy a small return pump, but what's confusing me is somtimes it works perfectly and returns exactly whats going in but on the other hand it somtimes like now its taking water from my sump more then whats going it
if someone know or have in countered that problem before please tell me
thankyou

How many liters is display tank?
You should shoot for 3-6x display tank volume per hour. Would agree with above statement about full siphon/no full siphon is what is causing fluctuations. Is it a single drain system?

 

[Supa]

+1 on what @T-J mentioned, also if your running filter socks or sponge filters etc they will slowly clog up and reduce the water going into the Skimmer / return etc.(meanwhile your return pump keeps pumping out the normal volume of water). Then your ato will turn on and pump fresh water into the tank throwing off the salinity slowly…. Keep an eye out for that possibly

 

[Water Dog]

Just to be clear, are you using an ATO? I’m wondering if it could be evaporation, which only affects your return chamber if you’re not using an ATO.

 

[\m/reefsnmetal\m/]

The only other thing I can think of that isn't mentioned is algae growth. If its growing in your overflow box or clogging the holes the water is supposed to flow through into the box, then it could cause the same issue you are having. I have to periodically scrub my skimmer box with a toothbrush or the water level in my tank rises.

 

[fishingchuck]

I have to clean the screens on my overflow/drain. They’ll start to grow algae and decrease flow to the sump. I try to clean mine off weakly to avoid any problems.

 

[CollectOyster04]

Just looked this up. It's definitely a simple cheap way to produce a durso type overflow. I personally am not a fan of a single point of failure. At a minimum, I run a herbie style (2 pipes), but especially with bigger tanks, my piece of mind is the bean animal way. Redundancy helps prevent accidents.
Is your return pump an a/c pump or a variable speed d/c pump ? A d/c style would enable you to throttle down a notch and should help solve some of the issue I would think. It could be that your pump may pumping just a bit more water than your pipe can handle. Did you make the updated version with the larger pipe to be made as a weir ?
A setup like this could be tricky to regulate because there just isn't enough control for the flow to the sump or return to the tank. It may take quite a bit of trial and error, and you may never be satisfied with the result.