Check Valve Question

[Th0r4z1n3]

I'm working on setting up an Algae Scrubber. I went to the hardware store today to grab all the piping & stuff I need for when my overflow box gets here, an have a question about the check valve I purchased. I know metal & saltwater don't mix very well, but the only check valve they had for my return line has stainless steal bits inside it; is this going to be OK or should I look around for something else?

 

[Bifferwine]

I have never been able to find all-plastic check valves locally. For all my tanks, I ended up ordering them online. Marine Depot has several types, check them out (here is one):

Swing Check Valve - Slip x Slip

I'm sure there are probably sites where you can find them much cheaper if you look around a bit.

 

[Th0r4z1n3]

THANK YOU! That is exactly what I was looking for, but the guy at the hardware store looked at me like I was speaking Japanese when I tried to describe it to him. He didn't seen to comprehend the idea of a "flap" inside a check valve. You're a life saver..or should I say a fish saver. : D

 

[bjohanson1234]

If set up right, IMO, a check valve is unnecessary. In order to keep water from back siphoning, just drill a 1/4 inch hole in your return line right at or under the water line. Then fill the tank up until the water starts to go down the overflow. Then fill the sump up to about an inch or so below the top of the sump. Turn everything on, let it run for a few hours to work any air out of the lines, then take a sharpie and mark the sump where the waterline is. If you keep the water at this level, then when the power turns off, the water will only raise up to about an inch below the top of the sump.

 

[Th0r4z1n3]

I've considered drilling a hole at the top of my return to break the back siphon, but I just can't seen to wrap my mind around it not squirting water all over the place when there is pressure. A check valve will just give me more peace of mind I guess.

 

[Bifferwine]

It won't squirt water all over the place, because you will drill it just below the water line.

 

[Th0r4z1n3]

This is for the line that goes from my Algae Scrubber up into my tank. so if I'm understanding this correctly, if I drill a hole right at or below the water line in my tank it should eliminate the need for a check valve in that line right?

I guess the reason I'm having such a hard time wrapping my head around it is because when I first envisioned it, I was gonna put it right at the top of the "u joint"that would take the pipe up and over the back of my tank.

 

[Bifferwine]

Yes, you drill the hole right at or below the water line. If the power goes out, a back siphon will start and water from your tank will drain. As soon as it drains enough so that air hits that hole, it will stop draining (that's why its called a siphon break). So if you put it right below the water level, it stops the back siphon almost immediately, without the need for a check valve.

 

[Th0r4z1n3]

Thank you for your help guys, and thanks for saving me $20 + shipping. : D