Need Advice - Connecting an External Pump to Wet/Dry Filter

[Chiselchst]

Hello everyone - I would appreciate some input on connecting a pump to a new wet/dry filter.

I need to drill a hole in the filter acrylic and install a bulkhead to connect the suction line to my new Little Giant external pump.

Are there any tips you all can provide? Do I want the pump to set on the cabinet bottom, or should it be attached to a peice of wood or anything? Should it be raised any?

Also, if I route the discharge line BELOW the water level, would a checkvalve prevent a siphoning back of the entire water level during a power outage, or should it be located above the water line...?

Should I use all rigid PVC, or flex?

I know, a lot of question, LOL.

All input greatly appreciated...I have never done this before.

Thanks,
Mitch

 

[jsoong]

I've never done it either, but I am setting one up & done a bit of reading ....

I personally will not trust a check valve to stop back siphoning when the pump stops. I tested a setup in my backyard, and with 1/2" tubing, the water was coming back at about 5 gal a minute when I shut off the pump ... won't trust any valve with that kind of flow. I am going to drill a small hole (say 1/8") an inch or so below the water line to proviode for a siphon break when pump fails, and of course I will make sure I have enough room in the sump for that inch of water.

Where to place the pump ... One consideration is what happens if your overflow quits. I would place the pump intake at a level so that if the overflow is plugged, the pump will run out of water to pump before it overflow the tank.

Rigid or flex ? I am using both, rigid for in the tank, & flex for ease of connection & ability to move things around in the cabinet during cleaning, etc. Don't know how that will work, let you know in a few months!

This series of articles had helped me in designing a sump/overflow system. You might want to check them out:

http://reefkeeping.com/issues/2003-01/gt/index.htm
http://reefkeeping.com/issues/2003-04/gt/index.htm
http://reefkeeping.com/issues/2003-07/gt/index.htm

 

[Chiselchst]

jsoong,

Very good points. How about if I drilled a hole above the water line, letting out a minimal amount of water during the pump running conditions, that would provide a siphon "break" if the power went off? That would *break* the siphon, thus disrupting the siphoning effect when/if the pump shut down?

That would allow the discharge to be routed below water, thus allowing IN air during a pump stop condition - breaking the siphon?

Comments?

Thanks,
Mitch

PS I guess the "safest" thing to do would be to have the pump discharge ABOVE the water level, maybe in a spraybar type arrangement, that would NOT allow the siphoning effect allowing the flow to back flow through the pump during a power outage?

 

[loganj]

Very good points. How about if I drilled a hole above the water line, letting out a minimal amount of water during the pump running conditions, that would provide a siphon "break" if the power went off? That would *break* the siphon, thus disrupting the siphoning effect when/if the pump shut down?

I'd put it just below the waterline. Only a small amount of water will back siphon if the pump quits and your sump should have the capacity to handle it. If you put it above the waterline, you're going to have problems with salt creep.

PS I guess the "safest" thing to do would be to have the pump discharge ABOVE the water level, maybe in a spraybar type arrangement, that would NOT allow the siphoning effect allowing the flow to back flow through the pump during a power outage?

Again, this will cause salt creep which is something you really want to avoid. I wouldn't put the pump intake up high either. It will likely suck air and fill your tank with bubbles. You'll have to have a few inches of water over the pump intake to prevent this. If you raise the level of the pump intake, you'll have to raise the level of water in the sump accordingly. If you have the water level in the sump too high, it won't hold the water that will drain down from the tank if the pump quits. Also, the chances of your overflow, if properly set up, clogging or losing siphon are pretty slim. If you need extra protection, there are pressure switches that will cut the pump off if the water level in the sump drops too much. I always like to sit external pumps on a piece of styrofoam as it cuts noise and vibration. I also would put a cut off valve and union between the pump and sump. I'd put another cut off and union on the pressure side of the pump as well. This will allow you to easily remove the pump if you ever need to. JMHO.