large overflows

[ebb]

I have a 240 reef ready with 2 1.5 inch overflows. These seem very large to me, I only want to have 800gph or so run through the sump, do I need to restrict these with ball valves or the like? Forgive me I have never had a reef ready tank with overflows like this. Seems that at that low of a return rate the tubes will be empty all the time being that that flow rate could far exceed the flow in the the overflow.

Maybe I just don't know how it works, can someone enlighten me?

[WaterKeeper]

Hi Ebb,

Not exactly sure how you have things plumped. I take it you have weir boxes of some sort. You never direct flow directly to a top drilled overflow without a weir or you would drain the tank pretty fast and free it of unsuspecting fish. :eek1:

The main problem with two big of a drain line is noise and bubbles. You get more turbulence in a partly filled pipe and it induces air in the discharge. Here I'd use gate valves rather than ball valves as they have better control if you wish to restrict flow.

[ebb]

I guess I have weir boxes, they are built into the inside of the tank. So you are suggesting gate valves just to keep noise down but not necessary otherwise? I was planning on using a durso standpipe there, which would prevent the siphon when the pump is off correct?

thanks

[WaterKeeper]

It should help and with oversize plumbing the gate valves can be included with no loss of overall head in the system. They are also handy when doing maintenance.

[Hop]

I have 1.5" and like them. For the 240, you should be able to do some tweaking. After messing with mine for a few months, they are totaly silent!

[fareforce]

My 500gal that is being planned is going to have 4 - 1.5" drains. I think 2- 1.5" drain is fine.

[WaterKeeper]

Me too. ;)

[poppin_fresh]

Remember... an overflow, no matter how big it is will only drain = to what the return pump is pushing. The fact that yours can handle more than you want is not a bad thing, it will keep them quieter.

You might even find that 800gph is too much through the sump, depending on the equipment and setup in it.

[Scuba_Dave]

I have (2) 1.5" drains on my 125g. I'm running a Iwaki 70 pushing just over 1400gph. The advantage of dual large drains is they can clog almost 1/2 way & still handle the flow.
Don't ask how I know this ;)
But a hint would be...if you are sitting down...and look up behind you at the tank....and the middle braces are under water
there IS a problem!!
Sooner or later I will complete the storage compartment beside the tank to hide the pipes & sound proof it
But before I do that I'm installing a larger sump, a smaller pump, and a 180g instead of the 125g

whatever you are pumping into the tank, is what will overflow & go down the drains