I built an overflow..Dilemma! Need help. Please!

[asudavew]

Hey everyone.

I am in the process of creating my first saltwater tank. A 30 gallon.

I have a 10 gallon tank below that I am going to use as a refugiam/sump.

I have 2 pumps that I can choose from: A pondmaster 500 gph and pondmaster 700 gph.

I chose the 500. Which, optimally, will turn over the tank about 17 times per hour.

The tank is not drilled, so I decided to build an overflow out of 1 1/4" PVC pipe.

It functioned fine, BUT, the pump blew the overflow away.

There is just no way that the overflow can keep up with the pump.

So what do I do now?
Go with a smaller pump? (I think the 500 is perfect, so I don't want to do that)

Build the overflow out of 1 1/2 " PVC? Does anyone think the 1 1/2 will work? Will it make that much of a difference?

So that's my dilemma.
Any help would be appreciated.

Thanks!

Here's a crude sketch in paint.

 

[MarineFlake]

You should always use a ball valve or really a true union ball valve, on your return from the pump. This solves two problems. First, your issue with controlling the return rate of the water, which as you have discovered, can over take your overflows feed rate. Second, a 'union' ball valve will add the ability for you to turn the pump off, close off the valve (Plumb it so the valve is tank side, not pump side) and disconnect the pump to be removed easily for replacement, repair, cleaning, etc. Going with a smaller pump or building a larger over flow are both options as well, it is a matter of what you are trying to accomplish. I won't get on my soap box here, but trying to obtain some astronomical amount of 'turn over' in the tank won't buy you much. I use a MAG 9.5 on a 135g tank and it has to be 'throttled back' (With a ball valve) about 75 percent, so Im probably not getting even 500GPH, yet my tank is doing just fine ; ) Ah, the myths of reef keeping...Anyway I digress, best of luck with your design, bottom line, my advice is to install a ball valve for various reasons.

GL!

 

[partypalooza5]

This may be a stupid question, but are you sure the overflow is primed all the way? If there's air in the "U" bend it doesn't work very well.. At least mine didn't.

 

[asudavew]

You should always use a ball valve or really a true union ball valve, on your return from the pump. This solves two problems. First, your issue with controlling the return rate of the water, which as you have discovered, can over take your overflows feed rate. Second, a 'union' ball valve will add the ability for you to turn the pump off, close off the valve (Plumb it so the valve is tank side, not pump side) and disconnect the pump to be removed easily for replacement, repair, cleaning, etc. Going with a smaller pump or building a larger over flow are both options as well, it is a matter of what you are trying to accomplish. I won't get on my soap box here, but trying to obtain some astronomical amount of 'turn over' in the tank won't buy you much. I use a MAG 9.5 on a 135g tank and it has to be 'throttled back' (With a ball valve) about 75 percent, so Im probably not getting even 500GPH, yet my tank is doing just fine ; ) Ah, the myths of reef keeping...Anyway I digress, best of luck with your design, bottom line, my advice is to install a ball valve for various reasons.

GL!

Thanks.
I was thinking about adding a valve. But I figured it would cut the turnover.....so your tank turns over less than four times an hour and no problems? I was just going with what I have read and some advice... 40 times an hour!! I was thinking, holey moley! My tank would look like a rushing river!l

I'm pretty sure I would have to cut the flow rate in half.. maybe 250 gallons per hour.. That seem like it would be ok to you?

Thanks for your help.

 

[asudavew]

This may be a stupid question, but are you sure the overflow is primed all the way? If there's air in the "U" bend it doesn't work very well.. At least mine didn't.

I drilled a hole at the top of the "U". Then I glued a check valve into the hole, attached a piece of air tubing, and sucked the air out to start the siphon.

After that, I attached the air tubing to a power head. So I assume that it was clear of air.

But I'll try it again tonight and see if there is still air trapped in it.

Thanks!

 

[gzeiger]

The change in piping diameter would be about a 50% increase in flow rate (45% increase in area, and also lowers the fluid friction). The first post made some good points too, but if it was at all close between pump and return the bigger overflow should do it.

 

[asudavew]

Thanks GZ.

I knew flow rate would increase by increasing the diameter, but I had no idea how much.
I think I will combine ideas and go with a 1 1/2" overflow, and add a ball valve to the return line.

Isn't it fun playing with fish tanks?
No one seems to understand but people here!
Thanks!

 

[partypalooza5]

Thanks GZ.

Isn't it fun playing with fish tanks?
No one seems to understand but people here!
Thanks!

My entire family thinks I'm nuts.

 

[asudavew]

This may be a stupid question, but are you sure the overflow is primed all the way? If there's air in the "U" bend it doesn't work very well.. At least mine didn't.

Went home for lunch.
Attempted to suck more air out of the "U".

Sure enough ... There was MORE.

Restarted the pump, and boy did it flow!
It more than kept up, it rocked.

Great advice! I do appreciate it.

I will probably still upgrade to 1 1/2" pvc.... Just for a little extra flow... (just in case)

Thanks again!

Dave