New Setup - Overflow Flowrate problems

6 Jul 2015
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Hi Guys,

I have just set up my marine tank.

I am running an overflow with 32mm piping.

I have been forced to throttle down my return pump flow as the overflow from the tank is too slow.

I am only getting a flowrate of approximately 250 lph and my tank size it +/- 550-600litres.

The level in my tank remains about halfway on the overflow outlet.

I would appreciate any advice if you've had a similar problem

Welcome to MASA.

Any pics will help the guys here understand what you have and they will be able to advise you accordingly.
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Thank you Gents.

I have a cube tank and the Glass is drilled with a 32mm hole for the overflow. PVC piping is connected straight from the hole to the sump with 3 elbows

I will take some pics to send and add them in
How did you adhere the fittings? Silicone? If so some has possibly squeezed into the pipework reducing the inner diameters? Check for that.
Thank you for the response.

I used pvc solvent to adhere the fittings. Thin coats on either side then stuck them together.

I have attached some pics of the overflow
Here are the pics. Hopefully they attach this time



incl waterflow, clogging- especially if a fish goes in. would atleast add a mesh infront, but since the flow is pulled into such a small area it might still grab onto a fish. Is it possible for you to add an inside box? and I would recommend a bigger overflow pipe?
Thanks for the advice. I'll add the mesh to the outlet.
The problem with adding a bigger Diameter pipe is that I'd have to drill a hole is the glass to increase the outlet diameter size. I could increase the diameter at the beginning of the pipe - not sure if that would help?

I wouldn't even know what to do in order to add a box lol
I thought of adding a power head or wave maker into the tank to increase the water circulation and reduce dead spots
Dont think its the size of your return pip 32 mm is big enough i think that your skinny overflow is the problem seems that its not big enough or its blocked
40mm should assist with the flow rate, better to be safe than sorry maybe try 2" or 50mm, as has been advised make sure to get some sort of mesh so you don't get a snail or something go down the hole. If you upgrade to 2" that no longer will cause any issues, but still advisable to stay with the mesh.

What works nice with the 2" piping is if you've ever bought plants for a fresh water planted tank, there are little pots that the freshwater plants are shipped in, these are perfect for using as a mesh/grid to stop blockages.$_35.JPG

The little black pot in the pic.
I thought of adding a power head or wave maker into the tank to increase the water circulation and reduce dead spots

Wavemakers are the way to go. You get many different types, depending on your budget...
I think the return pipe is too small. Best get it fixed now, before you cycle and stock your tank. Perhaps another 1 or 2 holes should be drilled lower down, then you can build an overflow box and get a good surface skim on the water. The original hole can be left piped up, possibly an emergency overflow.
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Thanks guys.

Seems like my tank was suffering from PMS.

Opened the pump full this morning and the overflow kept up.

Need to get a wave maker and skimmer now :(
There's going to be a fair amount of suction at the DT drain, don't forget to install some sort of mesh guard to prevent your fish from being sucked into the outlet pipe.
Although the hole in the glass is 32mm, the inside diameter of the bulkhead would be somewhere between 20 and 25mm.

Redrill another hole, and use the existing hole as the inlet would be a much better option. Set up a slimline overflow box in front of the outlet would help a lit. New outlet hole does not need to be that high then either.
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