my DIY PVC overflow, 1.5"

attach a barbed end to the ball valve if you are going to run hose to the sump. From what I'm seeing it looks like it should work.

what about the "flexible PVC" that uses regular PVC glue? anyone know if that's any good?

I saw some barbs at home depot but I didn't see any 1.5" elbow barbs ... or maybe I could get the 1.5" ribbed pool hose, i just wasnt sure how you attach that to the pvc

Maybe I'm missing something, but won't the air inlet on your overflow break the syphon.

maybe an expert could chime in, but I believe the point of the air inlet is to break the siphon (because if it siphoned all the way down it would drain water too fast). Since the "Wye" fitting is above the lowest part of the U on the inside of the tank then I believe it should maintain a siphon in that part of the unit

I'm curious, haven't tried one yet, Love the pictures :thumb: What's the ball valve for? If you slow it down, you'll flood the tank. Just for "maintenance" reasons? Looks like it should work fine.

well, i dunno what the ball valve is for I figured it would be nice to stop the water flow without breaking the siphon? if not, then I wasted $10 :lol:

i can't wait to try this thing out

If you don't have the air inlet side, it will draw air out the other end, along with all the water in the pipes. The middle portion will stay full of water this way, when the water spills in the intake side the level in the pipes will rise and just spill over the "Wye'd" pipe into the sump.

then I wasted $10

Click to expand...

No, nice addition. I just wouldn't stop the flow with the pump turned on
Looks like it should keep the "siphon" by itself, safe in a power outage. Can't wait to see how it works out.

yeah, you're right, that would make the water start rising rapidly in the tank

but, i think it would be nice for changing out filter pads? i don't know, i've never had any of this stuff before

so, flip the power on the pump off, and then immediately turn the ball valve or something? then ...don't forget to open it before you turn the pump back on of course

oh, yeah, i just realized that a second ago. your colored in drawing confirms my moment of enlightenment. i just thought about how it works and now it all makes perfect sense. so basically the ball valve is pretty useless

although maybe the ball valve could help make priming the siphon a lot easier...less air to suck out

ok new questions...didn't really want to start a new topic because it relates to this

should I get a Mag Drive 12 (1200 GPH) or Mag Drive 18 (1800 GPH)?
with a 5' head height and 2 elbows and/or a spray bar (haven't figured that part out yet), what do you think the flow rate would be then and could this theoretically handle it? :-?

oh and tank size will be 125 or 135

don't forget an air check valve in the loop going over the tank. If you don't get all the air out you run the risk of it losing siphon once the power is cut. monsterfishkeepers.com in the diy section has some 60 pages on building DIY overflows and different mods.

Craig

There was a link posted here that told how much flow you could get from different diameter standpipes, I can't find it :-?
Just go to MFK and type pvc overflow in the search box, hundreds of results come up :thumb:
I'm still looking...

http://www.reefcentral.com/calc/drain.php
http://www.reefcentral.com/calc/hlc2.php
FINALLY googled it up.

They've got some diy's there too, but it's a saltwater site.

yep, i added the checkvalve in. i think i'll attach it to a powerhead venturi to keep air bubbles out. will post some more pics whenever i get it running on the tank

i'm not sure what that drain calculator applies to? I think it applies to standard overflows and I'm betting these siphon types are somewhat less due to the number of elbows leading to more water resistance.

A check valve will malfunction eventually when used with a powerhead venturi. You only want air passing through the check valve. With a powerhead venturi, water will pass through the check valve and it will eventually get clogged. Then when air does build up in the overflow, the siphon breaks, the tank overflows, and someone will be mopping the floor. Believe me, I've tried it.

The powerhead venturi idea does work great without using a check valve. Just remove the check valve and fit the airline tubing right into that hole. You may have to open up the hole a little bit though. That's pretty much what I did and I haven't had any problems since.

hmm, didn't think about that. I guess it's because the checkvalve has a tiny opening.
I don't understand how you get the airline tubing to stay in the hole ? friction fit?

What about using a check valve and one of those "aqua lifter" pumps instead?