Overflow question

Mounda · 03/13/2010, 03:53 PM

I'm not quite sure which overflow design would work efficiently and at the same time be silent, I am mainly using the Herbie design but instead of using a stand pipe I'm drilling the holes on the back of the tank. Water should flow over my built in overflow box through the back of the tank and down to my sump. I'm going to use a single primary drain and will have an emergency drain just in case the primary gets clogged up for any reason. This overflow is for a 90 gallon setup so I'm looking for a 350-400 GPH flow rate.

I've take a few pics of the possible setups and would like some info on them. These are all gravitational overflows and there isn't any siphoning involved, there is no end cap or air hole either.

1)

Water flows down the primary without any air in the column and without any noise, should it malfunction the emergency would kick in causing a lot of noise to alert that there is something wrong with the primary.

2)

Without any extra fitting the water would flow through the bulkhead and down to the sump, a gate valve would be fixed to alter the flow if needed so the water level would be above the bulkhead and prevent any air from entering thus causing noise. The elbow fitting facing upwards on the emergency drain would grant a higher water level which would increase the water velocity on the primary and prevent air entrance.

3)

Providing the gravitational flow is enough, this should be a pretty easy design where water flows silently. No end cap or air hole is involved on the drain pump.

4)

This uses the same concept as option number 2 but without any fittings. I would use a gate valve on the primary drain(left) to adjust the water level between both drains.

Your input is appreciated.

Alex T. · 03/13/2010, 05:57 PM

You're going to get a lot of people telling you it's not good to have the pipe elbowed up in the tank like that; mostly because a snail or fish can get sucked in and cause an overflow. Personally, when I rebuild I'm going to do it just as you describe. My lfs has their reef tank plumbed this way and they've never had a problem in 15 years. Depending on the drain line you'll need for the return pump, bigger holes are definitely better. You don't lose anything by having a bigger drain hole than your pump can return. This is the only true way to guarantee no siphon. As for the position of the elbow in the tank...I've seen it two ways.

1. 90 degrees tilted upwards.
2. 45 degrees tilted. This way you could adjust the elbows as you see fit to accomodate what rate of water flow you wish to bring to the sump. To me, the plastic bulkhead strainer is a must in either application to stop a snail or small fish from "exiting" the tank.

Mounda · 03/14/2010, 03:04 AM

Yeah that seems like a good idea, I want to be able to benefit from the head accumulation above the primary outlet.

jacksonpt · 03/14/2010, 08:54 AM

There is going to be noise almost regardless. Why wouldn't you run the lower drain at full siphon and the upper drain at a slow trickle?

That said, if there is no air hole on the back side, it seems like 1 and 3 would give you problems with air getting trapped in the fittings and reducing your potential flow. I think I'd go with #2 with strainers on both.

Mounda · 03/14/2010, 02:14 PM

Yeah, I'm going with option 2. I reckon if I don't dial down the primary the water level will not rise above the drain outlet, the 1 inch drain is rated at 600gph and my pump will be running at around 325-375gph. I just ordered my glass today, I had the order of the holes swapped.

03/13/2010, 03:53 PM	#1
Mounda Registered Member Join Date: Aug 2009 Posts: 452	Overflow question I'm not quite sure which overflow design would work efficiently and at the same time be silent, I am mainly using the Herbie design but instead of using a stand pipe I'm drilling the holes on the back of the tank. Water should flow over my built in overflow box through the back of the tank and down to my sump. I'm going to use a single primary drain and will have an emergency drain just in case the primary gets clogged up for any reason. This overflow is for a 90 gallon setup so I'm looking for a 350-400 GPH flow rate. I've take a few pics of the possible setups and would like some info on them. These are all gravitational overflows and there isn't any siphoning involved, there is no end cap or air hole either. 1) Water flows down the primary without any air in the column and without any noise, should it malfunction the emergency would kick in causing a lot of noise to alert that there is something wrong with the primary. 2) Without any extra fitting the water would flow through the bulkhead and down to the sump, a gate valve would be fixed to alter the flow if needed so the water level would be above the bulkhead and prevent any air from entering thus causing noise. The elbow fitting facing upwards on the emergency drain would grant a higher water level which would increase the water velocity on the primary and prevent air entrance. 3) Providing the gravitational flow is enough, this should be a pretty easy design where water flows silently. No end cap or air hole is involved on the drain pump. 4) This uses the same concept as option number 2 but without any fittings. I would use a gate valve on the primary drain(left) to adjust the water level between both drains. Your input is appreciated.

03/14/2010, 08:54 AM	#4
jacksonpt Registered Member Join Date: Aug 2001 Location: Vestal, NY Posts: 3,679	There is going to be noise almost regardless. Why wouldn't you run the lower drain at full siphon and the upper drain at a slow trickle? That said, if there is no air hole on the back side, it seems like 1 and 3 would give you problems with air getting trapped in the fittings and reducing your potential flow. I think I'd go with #2 with strainers on both. __________________ Jackson - All advice I give is based on my first hand experience. YMMV. Current Tank Info: 38g (mostly LPS) with a 20g sump/fuge and all the other standard goodies

03/13/2010, 05:57 PM	#2
Alex T. Registered Member Join Date: Nov 2008 Location: New Jersey Posts: 1,803	You're going to get a lot of people telling you it's not good to have the pipe elbowed up in the tank like that; mostly because a snail or fish can get sucked in and cause an overflow. Personally, when I rebuild I'm going to do it just as you describe. My lfs has their reef tank plumbed this way and they've never had a problem in 15 years. Depending on the drain line you'll need for the return pump, bigger holes are definitely better. You don't lose anything by having a bigger drain hole than your pump can return. This is the only true way to guarantee no siphon. As for the position of the elbow in the tank...I've seen it two ways. 1. 90 degrees tilted upwards. 2. 45 degrees tilted. This way you could adjust the elbows as you see fit to accomodate what rate of water flow you wish to bring to the sump. To me, the plastic bulkhead strainer is a must in either application to stop a snail or small fish from "exiting" the tank.

03/14/2010, 03:04 AM	#3
Mounda Registered Member Join Date: Aug 2009 Posts: 452	Yeah that seems like a good idea, I want to be able to benefit from the head accumulation above the primary outlet.

03/14/2010, 02:14 PM	#5
Mounda Registered Member Join Date: Aug 2009 Posts: 452	Yeah, I'm going with option 2. I reckon if I don't dial down the primary the water level will not rise above the drain outlet, the 1 inch drain is rated at 600gph and my pump will be running at around 325-375gph. I just ordered my glass today, I had the order of the holes swapped.