So confused about outflow and Inflow

[BullyBee]

Hey now. I’m real good and confused about inflow and outflow. I will be drilling my tank (it’s all good. It’s not tempered on the sides).

Sooo do I want an overflow box that sits below my outflow bulkhead or equal to. I want as little noise as possible. I also want it to be as fail safe as possible. I understand all hoses returning to and going from the tank need to be same size. If my overflow is 1” and my pump is 3/4” a simple reducer will do...correct?

As for the inflow, what do I just drill a hole and install a bulkhead? Should it be lower or higher in the tank?

 

[reefwiser]

You want to purchase an overflow system that will give you a template on where to drill the holes in your aquarium.
you do not want the return line low in the tank. If you shut off the return pump the return will back siphon water back down into your sump.

 

[BeejReef]

This question comes up a lot. The hosing size really isn't a big issue. Only as much water as your return pump can push up into the tank can overflow back into the sump. The system is self stabilizing. The first time you turn it on, it will make perfect sense.

 

[BullyBee]

This question comes up a lot. The hosing size really isn't a big issue. Only as much water as your return pump can push up into the tank can overflow back into the sump. The system is self stabilizing. The first time you turn it on, it will make perfect sense.

So make the return as high as possible??

 

[BeejReef]

So make the return as high as possible??

Yes, you want the return as high as possible.
I used to have a link to a good youtube video on the mechanics of it all. Can't find it at the moment, but if you search, you'll come up with something similar. Here it is.. horrible video quality, but it made it click for me.


If the return is halfway down the tank, when the pump is off, your tank will siphon halfway to empty (likely overflowing your sump).

 

[BullyBee]

Yes, you want the return as high as possible.
I used to have a link to a good youtube video on the mechanics of it all. Can't find it at the moment, but if you search, you'll come up with something similar. Here it is.. horrible video quality, but it made it click for me.


If the return is halfway down the tank, when the pump is off, your tank will siphon halfway to empty (likely overflowing your sump).

Thank you so much! I know google and YouTube are always there but sometimes I just need human interaction because I can’t pause the video and ask them a question.

 

[BullyBee]

Wouldn’t a check valve placed high prevent water from siphoning in?

 

[BeejReef]

Yes, it would, but they can and do fail. Once your tank is fully set up with seemingly dozens of cords and dosing tubes, you'll be surprised how difficult it can be to get halfway behind it and to wrestle apart pvc or tubing with 2" of clearance between the tank and the wall to service a check valve. Probably a healthy percentage of us are guilty of neglecting check valves.

Also, with the return appreciably low in the tank, the water column will exert real pressure on the check valve. It wouldn't be operating (in that instance) simply as a siphon break. It would always have 30 or 50 gallons of water pushing on it, trying to get out. Imagine drilling a 1/2 hole in the side of a full bucket and holding your hand against it to prevent leakage. Anything less than a perfect seal (salt creep, tiny shell, sand) and water will make it past the valve slowly like a dripping faucet.

You'll notice that even on your gate valves and ball valves that cranking them totally shut usually won't stop a slow trickle when they're under pressure.

That certainly wouldn't be an issue when feeding or doing an hour of maintenance, but if you lose power overnight or while visiting family for the holidays, your display tank could very slowly drain out.

 

[BullyBee]

Yes, it would, but they can and do fail. Once your tank is fully set up with seemingly dozens of cords and dosing tubes, you'll be surprised how difficult it can be to get halfway behind it and to wrestle apart pvc or tubing with 2" of clearance between the tank and the wall to service a check valve. Probably a healthy percentage of us are guilty of neglecting check valves.

Also, with the return appreciably low in the tank, the water column will exert real pressure on the check valve. It wouldn't be operating (in that instance) simply as a siphon break. It would always have 30 or 50 gallons of water pushing on it, trying to get out. Imagine drilling a 1/2 hole in the side of a full bucket and holding your hand against it to prevent leakage. Anything less than a perfect seal (salt creep, tiny shell, sand) and water will make it past the valve slowly like a dripping faucet.

You'll notice that even on your gate valves and ball valves that cranking them totally shut usually won't stop a slow trickle when they're under pressure.

That certainly wouldn't be an issue when feeding or doing an hour of maintenance, but if you lose power overnight or while visiting family for the holidays, your display tank could very slowly drain out.

So even using a ball/gate valve and a check isnt even 100%.
I notice on my planted tanks water sometimes crews past the check valve for my co2. I have to turn the co2 on (timer does it actually) for the water to be pushed out

 

[BeejReef]

Well, ball valves and gate valves may not seal 100% tight, but they can't really fail to strictly regulate flow. They can't fail open. A check valve potentially could. If you have a really compelling reason in mind that you want your return flow lower in the tank, it's not against the law or anything... lol. It's just that a lot of people appreciate redundancy. If your return line is up high in the tank (barring the tank breaking or leaking) the tank level will never drop lower. Even if your sump broke or you reverse siphoned your whole sump into your freshwater top off, you would still have a display tank relatively full of saltwater.

If it's the flow you're wanting down lower in the tank, there are ways to accomplish that with loc-line and air holes for siphon breaks, but you'd still want to drill the tank up high. If you like the idea of providing flow with a pump instead of powerheads, you could also look into a closed-loop system.

The key difference there is that there is no where for the water to drain to. It's all sealed up. That's why you'll see some systems with holes drilled down low or even in the bottom.