Building PVC overflows today...flowrate/pipe size/# of overflows question

[Moloch]

I've recently set up a 55g saltwater tank...my first foray into the salty side of things. I've picked up a 20l sump & I have a quietone4000 pump. The pump is rated at 991gph, I'm assuming thats without any head loss. I'm planning on building the overflows today.

I've decided to go ahead and use the PVC overflow in the sticky, I'll copy the picture here just for clarity.

Now, I'm pretty sure that I want at least 2 overflows for safety's sake...if one clogs I still have a second going. Since my pump has 1"mpt already, ideally I think I would stick with 1" plumbing throughout. Going off the charts in the sticky, it looks like my maximum flow through a 1" overflow is 600gph. Based on that, should I actually go ahead and build THREE overflows? Or will one of these be able to keep up with my pump in the event of a clog?

edit: I should also mention, I'm considering using flexible tubing between the overflows and the sump. The sump is currently sitting on the floor next to the stand as I don't think it will fit well in the stand (I actually need to go play with that right now). I just think it might be easier to deal with flexible tubing for now rather than hardplumbing that.

Essentially: Will a single 1" pvc overflow keep up with a quietone4000 (990gph) pump?

 

[Bridger]

You could also modify how deep your pump sits in your sump in case of an overflow malfunction. I have mine set up to where if the overflow fails the pump can't draw enough water to overflow the tank. I think that ideally you want your overflow to outpace your return pump so that it never runs dry unless there is a malfunction. Even if one overflow fails you should still get enough flow to keep your pump from running completely dry and burning out.

 

[Moloch]

Yeah that's what I'm asking...are two 1" overflows enough so that if one fails everything still flows, or do I need 3?

If both/all of them fail and the pump runs dry, that's a different issue and there shouldn't be enough water in the pump chamber to overflow the tank...bu that's a different issue and kind of irrelevant to how many overflows I want/need.

 

[Oughtsix]

I have a quiet one 4000 and a 1" overflow pipe. The 1" overflow pipe is just big enough to keep up with the Quiet One 4000. If I weren't planning on drilling the tank I would make a single pipe out of 1.5". My 1" pipe has two inlets. One slightly lower than the other. If the lower main inlet plugs the higher one will take over. I just put a T fitting a couple inches below the water line to make the second inlet.

 

[Moloch]

Not a bad idea. I was about to respond with 'what happens if it clogs somewhere AFTER the inlet?' Then I realized the ridiculous improbability of that and laughed at myself. I might have to go ahead and do it that way then.

So I'll start with one 1" overflow with two inlets for backup. I'll put a ball-valve after the return pump with a T fitting sending a return with a ball-valve back into the sump, I can control the flow easily with these two valves. Sounds like a plan to me. Just gotta decide what I'm going to use for the pump return inside the tank...I have a few random things laying around or I'll just do straight PVC.

 

[epond83]

Something to keep in mind is when you flow near a pipes max it will be louder, so having extra flow 'space' as you plan is a good idea for noise. i would just consider upping the pipe size. The straight pipe is cheap and the connectors would be the same price if not cheaper given the numbers.

 

[Moloch]

Ah interesting, didn't know that. If I use two 1" overflows, will it be as effective in that regard as using one 2" overflow?

I already feel like a 1" overflow is going to be huge hanging in the tank, so I would really be dreading having to deal with anything bigger :\

 

[epond83]

with pipe sizing flow it's based on area not dia.

2 1" 600+600= 1200 gph
1 2" 2400 gph

Another option is to drill the tank which gives you more options