Balancing Sump

[fishgate]

I am having the hardest time balancing my new sump. Too much return flow and the sump gets low on water and micro bubbles come out of the return. Not enough return flow and the sump fills too high with water. It could be set ok and balanced and then a few hours later the sump is low again.

Is there some trick to this?

 

[billdogg]

I'm not sure I understand the problem. The sump can only fill/empty as fast as the pump/DT return drains can function

 

[fishgate]

Right - So if I have the return pump cranked up too high (via the ball valve) then the sump runs low (flows more than the overflow can empty so the return chamber in the sump gets low and lots of bubbles get returned as the pump sucks air).

If I turn the pump return flow down, the sump overflow is greater than the return pump and the sump fills with too much water and reduces the tank water level.

I occasionally get the balance pretty good and it runs for a day or so with no adjustment needed. But usually once the water level decreases due to evaporation, the balance is thrown off and I have to go through the whole ordeal again. I have no room for an ATO.

 

[rovster]

Sounds like you don't have enough water in your system. Unless you're running a BEAST of a return, just add water to the sump until it stabilizes. This is all assuming your drain can handle your return.

 

[Playa-1]

It sounds like you may be pumping more then your drain can handle or you may have some issues with the drain.

 

[fishgate]

return pump = 700gph (not adjusted for head height), overflow = 300gph. I think one problem with the overflow is that it flows more water the higher the water level is in the tank. The skimmer teeth are around 1/2" - 3/4" under the water line. So if there is a lower water level, it flows slower (less), if there is a higher water level, it flows more. It is kind of a viscous cycle. If I up the return flow, the water level rises and the overflow drains faster since more of the teeth are further underwater hence more flow.

I'd love to just drill this tank and do away with the unreliable nature of HOB overflows but with it up and established, I don't see that happening. Ideally I'd like to bottom drill it.

I guess I could lower the skimmer into the water more for faster overall draining.

 

[sirreal63]

Let's start with a list of the equipment involved. What is the pump and what overflow do you have? I am no good ad guessing.

 

[fishgate]

Sorry -

HOB Overflow - EShopps PF-300 (300 gph)
Return Pump - Mag MD7 (700gph)
Head Height - ~3 feet

 

[Big Dog]

I think the first 2 gph rates answer ur question? Return isn't large enough. That pump will do over 400gpm at that head.

 

[fishgate]

Yes, but I have a ball valve and am reducing it to match the flow. I don't think you'd ever be able to get a perfect match so overspecing the pump and reducing flow is the best choice.

 

[sirreal63]

A ball valve is a poor choice but it is what you have, you need to reduce the flow far enough to allow the 300gph overflow to operate properly, that could be as low as 250gph. It is a balancing act, too slow and air bubbles can collect at the top of the tube, too much and the overflow won't keep up. The ball valve doesn't allow very fine control, a gate valve would be the proper choice.

 

[fishgate]

I think the big question is where do I position the overflow skimmer? Do I put the bottom of the teeth at the level I want the water to remain at or do I raise it up? This overflow flows dramatically different rates depending on the amount of tooth slot below the water line. If you put it as low as possible in the water It will flow enough to remove the air bubble in the overflow tube. Anything less than that and the tube has varying amounts of air in it.

Look at the below video as I raise and lower the skimmer box.

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[Playa-1]

What size tank are you using for the sump?

 

[fishgate]

It is an Eshopps RS-100 20 gallon sump. Its running volume is a little under 10 gallons. so 11-12 gallons of extra capacity.

 

[sirreal63]

You set the level of the inside box to the level you want the water in the tank, then let it equalize. Slowly increase the pump out put so that any bubbles that accumulate flow through the tube. You may find it very hard to do with a ball valve, the adjustment is just not fine enough for that low gph of overflow. Too much flow, tank overflows, too little flow, bubbles accumulate and tank overflows. A ball valve is just not the right valve for fine adjustments, you may get there with it, but it won't be easy.

 

[Playa-1]

I suspect that Jack is right on the gate valve option for your situation. It would also appear that you may be running your sump to low. I can't think of a good reason to only be running 10 to 12 gallons in that sump.

 

[tomservo]

You could increase the capacity of that overflow by changing out that wimpy looking siphon tube with something bigger - I have made many an overflow tube with some PVC and 90 degree elbows. See if you can fit 1 1/4" or 1 1/2" in there and still have room for the water to flow up and around it. I would drill a small hole in the "arch" and glue in a cheap clear plastic check valve for starting the siphon (PVC glue).

One thing you need to make absolutely sure of is that your sump can hold all the water that will drain down in the event of a power failure!! I have seen guys that didn't consider this, power goes out for 5 minutes and saltwater everywhere, plus the pump is sucking air right after the power came back on and it pumped most of the water back into the tank.

 

[fishgate]

You could increase the capacity of that overflow by changing out that wimpy looking siphon tube with something bigger - I have made many an overflow tube with some PVC and 90 degree elbows. See if you can fit 1 1/4" or 1 1/2" in there and still have room for the water to flow up and around it. I would drill a small hole in the "arch" and glue in a cheap clear plastic check valve for starting the siphon (PVC glue).

One thing you need to make absolutely sure of is that your sump can hold all the water that will drain down in the event of a power failure!! I have seen guys that didn't consider this, power goes out for 5 minutes and saltwater everywhere, plus the pump is sucking air right after the power came back on and it pumped most of the water back into the tank.

No I don't think the overflow can flow any more than it is. Even with full flow - that is with the skimmer part allowing as much water as it can over the edge, the siphon tube barely keeps up. It always has a bubble even if it is almost all the way down the tube. I could take the skimmer off and it wouldn't flow anymore.

Also that sump has a water level mark which is right at the sump level. It is designed to hold exactly as much as the water level that I am keeping it at. Take a look at the picture and notice that blue box right below the black sponge - that is the desired water level. It could hold a bit more, you could go up to the top of that baffle I suppose but that is only around a gallon or 2 more of capacity.

I did test breaking siphon and the tank can hold the sump water and I also turned off the pump and the sump can hold the tank water that would drain. Probably also why this sump has so much extra space. So I am covered there.

I think I may just invest in another overflow. I like the CPR overflows they seem to be of a better design.

I'd love to bottom drill the tank but it is already set up and I really have no place to temporarily hold anything while the tank is being rebuilt. I do have a 120g FW tank that will eventually be re-purposed as SW. That one will be drilled and setup properly for a sump when the time comes.

 

[Playa-1]

I suspect that as long as the sump will hold the backflow when the power is off, Then you could run the water level considerably higher then it is. You may want to consider moving the the little blue mark that you're referring too.

 

[bravanc]

Looks like you have a 1" u tube and the tube to your sump is 1" too. You have created a full siphon and the 1" at full siphon can handle up to 960 gallon per hour tops. I would put a valve on the bottom of your over flow or input to your sump and adjust it there. You will be able to match the mag 7 flow.