Help 92 gal Tank Sump

[underwaterforest]

I still wonder about the flooding potential of a under tank sump. I just can't visualize how a gravity feed system would stop if the return pump became clogged or the power went out. I assume it may have something to do with the partitions in the sump setup or possibly the water pressure from the sump itself but I just don't get the physics behind it.

Does anybody know how to avoid flooding in the design of a sump?

[Eddie]

I still wonder about the flooding potential of a under tank sump. I just can't visualize how a gravity feed system would stop if the return pump became clogged or the power went out. I assume it may have something to do with the partitions in the sump setup or possibly the water pressure from the sump itself but I just don't get the physics behind it.

Does anybody know how to avoid flooding in the design of a sump?

I think that is the main pitfall in sumps but I am sure there are some sump gurus out there that can help you out.

[Jhhnn]

It's not about the pump at all, but about the sump capacity. When the pump stops, the water level in the upper tank falls to the depth of the comb in the overflow weir and stabilizes. The water that flowed out raises the level in the lower tank, the sump, but not to the point of overflowing... I routinely shut the pump off, let the sump ovefill when I start a water change, fill back to the bottom of the weir comb.

At startup, the sump must be slightly overfilled so that the pump will raise the water level in the upper tank somewhat while the inlet remains submerged... This is somewhat greater the higher the flow capacity of the pump. equilibrium is reached when return flow balances against pump delivery.

It's a function of the relative surface area of the two tanks and the depth of the sump tank. My 18"x48" tank and 12"x24"x17"T sump came as a set, a system, and there's plenty of safety factor in the sump size... At that 3:1 surface area ratio, every 1/4" of water level over the bottom of the weir comb lowers the sump level by 3/4".

Capische?

Most sumps have a provision to introduce air from a pump into the bioball chamber, particularly if there are tight fitting lids...

[underwaterforest]

Capische?

Yes I finally get it. I never noticed that the black piece of plastic in the back of the tank is a weir setup, I just thought it was a direct connection to the upper aquarium water level. I guess I have to look at things more carefully. All I have to do now is get a big enough sump to deal with the potential for pump failure which should be easy to calculate.

Another idea to that came to me to allow a smaller sump is to add a sealed inlet tube near the surface of the aquarium. Depending on the distance from the surface to the tube I can therefore vary the volume of the overflow from the tank. Thanks Jhnn, I can sleep easy now.

Most sumps have a provision to introduce air from a pump into the bioball chamber, particularly if there are tight fitting lids...

Good advice, I might add a venturi fitting or a air pump to make sure the aerobic bacteria is happy. I just have to find a quiet method to add the air, my girlfriend is a little overwhelmed by all the aquarium noise already in our living room.

[caparzo]

I didn't know it was called a " wier " set up. But yeah.. it shuts itself off.

[Jhhnn]

Yeh- it's important that the pump output to the upper tank be at or above the water level of the weir, or at least be drilled with a big enough hole to break siphon, prevent backflow...

Forgot to mention that... mea culpa...

I'm not sure "weir" is the correct term, but it got the point across...

[Dkarc@Aol.com]

Most sumps overflow because the return line plumbing (black loc-line fittings mostly) are kept under the water line to minimize noise and air intake. When the pump turns off, the water begins to flow backwards through the pump housing itself and since the return plumbing is underwater it begins a siphon. How much water drains back into the sump depends on how far underwater that fitting is. Basically you have 2 options to prevent sump overflow due to pump/power failure.

#1: install a swing check valve. Work great and well worth the money. Very reliable and easy to install. Not always easy to find though. Prevents the backflow of water through the pump.

#2: In the overflow box/weir setup in the tank there are 2 holes. The larger hole is the drain leading to the sump, the smaller is the return line from the pump back into the tank. At the top of the return line plumbing you will be installing a 90 degree elbow so that the water points back into the tank itself. At the "crotch" of the fitting drill a small 1/8" (approx) hole into the 90 degree elbow. This will act as an anti-siphon hole. How this works is when the pump shuts off, the water begins to flow backwards through the pump due to gravity. As the water flows back, air is drawn into the line via the anti-siphon hole. As more water flows backwards, more air is drawn in. Within seconds of this flow starting, enough air is in the pipe to disrupt the flow of water and breaks the siphon. Very effective and extremely cheap/easy method to use. However it is not fool proof as overtime algae and other gunk can clog the hole. So long as you keep it clean it'll work just fine.

-Ryan

[Jhhnn]

With the pump output in my setup, I plumbed it across the top/back of the tank to the corner opposite the overflow, suspended it in place with some fabbed up stainless steel clips. Theres an elbow and short length of pvc pointing straight down. Just upstream of the elbow there's a 1/4" anti-siphon hole, right on the bottom of the pipe, still above the level of the overflow.

This gives me the laminar flow I want across the bottom, pushing detritus to a place on the bottom near the overflow- makes cleaning up easy, gives good flow with low turbulence in the main part of the tank...

[underwaterforest]

Without a doubt I will put a anti-siphon coupler on the output, it would be a bummer to lose my carpet to a overflow. The other things I need to buy at the hardware store are a pair of valves to control the output/input to the sump and also some 3/4" pvc pipe or larger for the plumbing work. I'm still thinking if I can find a 20 gallon glass tall aquarium or just a plastic tub that would be prefect. I like the idea of the glass aquarium for a sump both for ease of cleaning and also for the ability to place the heater into.

I'm still toying with the idea of putting plants into a middle partition in the sump. The plants would be great for the removal of nitrates/nitrites and ammonia for the water stream. It may cause a little more maintenance for the system with the plants though. Another option is to use the ammonia/nitrate/nitrite removal crystals in a pre-filter for the sump.

[Jhhnn]

The drain line from the upper tank to the sump really shouldn't be valved, at all, and is generally 1" pvc or larger, depending on pump output. It also needs to be a continuous downhill run, without any sort of low point or trap. submersible pumps are the easy answer, and can be valved on the output to regulate flow. External pumps require drilled sumps and bulkhead fittings. They're generally used in marine aquaria where heat transfer to the water is undesirable and where heat output from very powerful pumps is high.

Might want to explore sump design a little more before moving ahead, also investigate algae filters. There's a thread somewhere here about them, and the whole concept seems sound enough...

[underwaterforest]

Jhnn thanks for the suggestions, but I don't really see why I can't use valves on the output/input of the sump. Without valves how to you stop the water flow when you have to clean the sump? Do you have a reason why you believe the valves get in the way? Flow restriction? I'm not too worried by the DIY part of the sump design, it's the fun part. Pump filter bags are standard for me when it comes to water pumps so clogs should be minimal on the return pump end. I'm thinking of going rather cheap and simple with the design, after researching many different designs from commercial to DIY. After all freshwater sumps are really just big media boxes and not that complicated, I just have to keep myself for over thinking this simple project. I ordered 4 bags of the bio-bale for media and new bulkheads for the tank. I just have to get back home so I can find a plastic tub that is appropriate sized and another smaller tub for holding the media. I'll probably with use some cheap filter floss (pillow batting) as a initial mech filter/bio and then spray onto the bio bale. Let you all know how it goes when I get to start the process.

[Jhhnn]

I apparently misunderstood your reasons for having a valve in the return. If it's just for service, no problem. If the return gets clogged for any reason, then the system can flood over the rim of the main tank, particularly with a large sump. Large open returns also help prevent gurgling...

When I need to deal with the sump, I just turn off the pump, wait several minutes to let the system drain down into the sump, at which point no more water flows. I do that for water changes. Pulling the prefilter sponge and siphoning a little more water out of the overflow chamber stops dripping when and if I need to remove the sump entirely...

[caparzo]

My sump for this tank looks like this...


Looks like my biowheel needs a cleanin..

[underwaterforest]

Thanks Caparzo, I like the simple design of your sump, very functional. I'm thinking of something very similar to yours. I am still traveling so I haven't had an opportunity to start the sump project, but soon I will. Tomorrow I might have to give Kenny a visit since I'm in his neighborhood.

[jeff@zina.com]

Many sump users will plumb a sump overflow to a drain. That way, the sump only fills to a point and anything else goes down the drain. Note that this doesn't work if your return pump from the sump to the tank has an outlet near the bottom of the tank. If it does turn into a reverse siphon, you won't soak the carpet but you will drain all the water from the tank. Discus don't like having no water...

Jeff