Drain Dip?

[springsreef]

Anyone ever seen an aquarium drain that didn't go down hill the whole way? Obviously the beginning has to be higher than the end, but what if there were a "dip/trap" somewhere along the way.

I'm faced with a situation where I'm tempted to do this. I'm wondering if it's going to be a total disaster. I'm hoping that adding a "vent stack" right before the dip will let the air out and keep things moving.

The Details:
The drain pipe has to pass into my garage through an opening that is about 3" below the lip of my sump, but the sump is still a good 5' below the tank. So I'm gonna have this low spot in the plumbing. I'm worried about air building up and creating back pressure, until the level in the tank overflow chambers gets high enough to make a siphon and then cycling like that forever.

Any plumbing experts in the house?

[Fat Tony]

Shouldn't be an issue as water will always find its own level. Meaning, that whatever the water level is before the dip is what it will maintain during draining, once water flow stops a little water will remain in the dip but the rest of the pipe will be clear of water without an issue.

[springsreef]

Originally Posted by Fat Tony

Shouldn't be an issue as water will always find its own level. Meaning, that whatever the water level is before the dip is what it will maintain during draining, once water flow stops a little water will remain in the dip but the rest of the pipe will be clear of water without an issue.

Yeah, I know that water will flow through the drain, my question is will it flow fast and steady like I want. They would never do this kind of thing in a household drain, but maybe in this application it will be okay... I just don't know.

[Fat Tony]

Yes it will be fine.. they do it every day in household drains... look under your sink, then go look at you plumbing from your bathtub under the house...

[mxracer19]

Yep, its called a trap. It allows the water in the low point to block the foul smells from the plumbing below. You may have to use a larger drain pipe to overcome the bend but eventually your water level will reach equilibrium.

[Elegance Coral]

If I understand your post correctly, you're worried about the water flowing uphill over the lip of the sump, then back down into the sump. Not the low point or "trap" portion of the plumbing. Am I even close?

With 5' of drop you shouldn't have any real problems. If the discharge of the drain pipe is under the water of the sump it will put some back pressure on the system as it is forced to push air bubbles below water level. This usually isn't enough to be concerned about though. If you want to insure that this doesn't become an issue, you can put a vent at the peek of the plumbing where it goes over the side of the sump or keep the discharge into the sump above the water level. This will allow air to escape the system without adding back pressure.

[springsreef]

Originally Posted by Elegance Coral

If I understand your post correctly, you're worried about the water flowing uphill over the lip of the sump, then back down into the sump. Not the low point or "trap" portion of the plumbing. Am I even close?

With 5' of drop you shouldn't have any real problems. If the discharge of the drain pipe is under the water of the sump it will put some back pressure on the system as it is forced to push air bubbles below water level. This usually isn't enough to be concerned about though. If you want to insure that this doesn't become an issue, you can put a vent at the peek of the plumbing where it goes over the side of the sump or keep the discharge into the sump above the water level. This will allow air to escape the system without adding back pressure.

Exactly what I was looking for, thanks!