Overflow/siphon system

[jeremy arsement]

Got a120 gal with 15 gal sump, having trouble with the overflow being too slow. It won't keep up with my pump. Need some design ideas.

 

[Monsieur Kam]

- Try letting more water into the overflow if possible (lowering it inside the tank)
- If there is a sponge (prefilter) in the overflow in the part outside of the tank try taking that out to get more flow.
- Add a second overflow
- Add a smaller pump

How many GPH is your pump rated?

 

[Rscomia]

Can you post a pic of your overflow?

 

[jeremy arsement]

Don't wanna lower the pipe, that could overflow my sump if I lose the pump for some reason. Im using two 1 inch PVC pipes, each has 1/2 inch nylon tubing for the siphons. Both drain to a single overflow with a 3/4 in drain down to the sump.

 

[jeremy arsement]

Pump is rated between 400 and 800 gph. It's adjustable.

 

[jeremy arsement]

I'll get a pic up in a few days. Outa town right now.

 

[Rscomia]

Here is one I built myself from pvc http://www.aquariumadvice.com/forums/f20/diy-pvc-overflow-153636.html
It keeps up with my pump that is 1384 gph

 

[jeremy arsement]

So how does the water enter your sump? Does the 1 1/2 in line extend below the water line of your sump? Also, explain to me the siphon break.

 

[Rscomia]

It flows as a siphon over the back of my tank to the sump which is underneath my dt and I just run it into the top of the sump A siphon break is usually a small hole drilled just below the water line of the tank(mine is in my return) which will allow air in if you have a power outage or pump failure breaking the siphon and keeping it from draining the water all the way down to your return

 

[jeremy arsement]

Don't you want to keep the siphon primed for when the pump comes back on? Otherwise you could over flow the tank.

 

[Rscomia]

The siphon break is for your return if the power goes out your return will become a siphon and flow back into your sump to my siphon will only drain to the bottom of the screens and will stay primed mine has always restarted itself every time it has lost power you can build this to set at whatever height you want in the water

 

[jeremy arsement]

Ok, I get it. I have a check valve on my return line so I don't need a siphon break.

Now I'm wondering if I need 1 1/2 in pipes or maybe just 1 inch since my pump isn't as powerful as yours.

 

[Rscomia]

I started with just one pipe but was not getting enough flow out of my tank so I added the second one So you might try it with just one keep in mind you can always put a ball vale in line to slow down the flow if needed

 

[jeremy arsement]

Cool! Thanks for the advice.

 

[Rscomia]

No problem Im not a expert on it but will try to help anyway I can

 

[David S]

Can you explain better the overflow box and pipework more clearly,flow rate from the overflow is governed only by 2 things.
1 return pump flow
2 overflow drain line.
If your overflow cant keep up with your return pump then the overflow box will submerse totally under water because more water flow is being pump up unless its emptying your return section of your sump.
Dont ever put any valves on the drain pipe from your overflow box,this can get blocked easily by algae or crap from the tank.if you want to slow the flow add a valve to the return pump pipework and throttle it down( normally pumps have a valve built in).Be careful doing this though, you need to keep the flow rate going through the box as close to its potential flow rate.this all needs to be considered when adding all this
So tell us what pump gph at what head loss on your system
what overflow box,and drain pipework sizes down to the sump.

 

[jeremy arsement]

My overflow box is pretty simple. It's just a one gallon pitcher. Used 3/4 in PVC for the bulkhead fitting and drain line. Have 2, 1/2 in vinyl tubing running to it. Each coming from 1 in pipes in the tank.

 

[David S]

any chance of a photo?

 

[jeremy arsement]

Here's the photos of my current overflow. In the process of redesigning it. It can't seem to keep up with my pump.

 

[David S]

well for a start you have a pump which pump up to 800 gph and a drain pipe which can only handle 660gph,you need to up grade your drain pipe to at least 1".You also have 2 1/2" hoses which are easily blocked and will cause you problems later,change these to 1" hose or try to buy just the syphon pipe from lets say an eshopps.These overflows also work very well and are quite reasonable to buy.It is imperative that an overflow syphon is built correctly if your going the DIY route,You could even make the u pipe with 1" pvc using long radius bends to help with flow rate.
So
1. the drain pipe must be rated at a higher flow rate then the syphon pipe/pipes
2. The pump after head loss should be rated at a maximum of just below the gph of the syphon pipe( if pipe is 800 gph get pump after headloss pumps 750gph)
3. the pump after headloss minimum gph should be no lower than 85% of the syphon flowrate(if syphon pipe is 800 gph then pump minmum gph is 680)
4. You can put a valve into the return pipe to throttle down the flow but never put one in the drain pipework.

The flowrate going through the syphon pipe needs to be as high as possible so the flow pushes any bubbles through the the other side otherwise an air break will occur and flooding.
hope I've explained this enough for you
David