Question about flow through the sump

[bbhs23]

I am in the very begining stages of designing my new tank and I had a question about the return flow. I know it should be 3-5 times the tanks volume, but is that only for the display tanks volume or does it include the sump/fuge/frag tank? My display tank is going to be 250g, but the total volume will be around 500g. So should the return flow be 750-1250gph (3-5 x 250g) or 1500-2500ghp (3-5 x 500g)? Thanks!

 

[kraze3]

I think around 300 is fine. My return pump is close to my skimmer pump. There was a large thread here about doing this so that more water will be skimmed.

 

[Laddy]

Some tough questions.

First, do you mean 3-5x volume of water (as in the size of your sump), or do you mean 3-5x the flow the sump will recieve? If you're talking about the size of the sump I don't think anyone would argue that bigger is better--get away with whatever you can fit under the tank, or remotely.

If you're talking about the flow rate of the sump, that's open for a lot of interpratation. 3-5x is really dependent on the performance of your skimmer, and how long you want the water to stay in contact with it. This of course is predicated on the strength of your return pump. You can either order an "under-powered" return pump, or throttle down a bigger one. I like a low flow return, mainly b/c I have a high bioload on my tank and requre some efficiency from my skimmer. Also, a don't throttle back pumps anymore--high heat, premature breakdowns, etc, etc.

And of course, all this is predicated on the number of return lines and the capacity of the water to drain from your DT.

Hope this helps.

 

[luther1200]

What is the flow rate trough most bulkheads? I have a 1" bulkhead and I think its 600gph is that correct?

So what would it be for a 1.5" bulkhead?

 

[drdavethedude]

I emailed the WetWebMedia guys about this subject a few months back and they say that rated flow rates for various size drains are grossly overrated. Typically its claimed that a 1" bulkhead will pass 600 gph but actually, under typical conditions, it's about half that. A 1.5" drain pipe is often claimed to pass 1200-1500 gph but again, its actually only about half that. The claimed numbers can only be remotely achieved if water is pressure forced through the piping, but normally this is not what is happening in your typical gravity fed overflow. Hope this helps.

Dave

 

[blakeorme]

While some definitely debate this method, its worked very well for me and I have had little to no issues. Google "The Herbie method" of overflow design. There is a long thread on RC about it. Whether or not you use it, the more info/perspectives the better when designing.