I am plumbing a Sequence 4300 (4300 GPH) closed loop system on my 120. The pump will be plumbed with 2" PVC with the suction/intake side being fed by an over the tank rim pipe. In other words, I don't have a hole drilled in the back side of the tank to serve as an inlet for the suction side of the pump. I purposely designed my system this way so that I wouldn't have to worry about a bulkhead leaking and draining the tank. The problem is that I don't know how low (how far under the water) I need to put my intake to keep it from pulling a vortex and cavitating. Is there anyone that has any experience with a system like this and can give me a rough estimate. I don't want to put it lower than it needs to be becuase the lower it is, the more the tank could drain if I had a plumbing leak in the closed loop system. There should be a way to calculate the minimum depth using the kinetic viscosity of sea water, but I can't seem to find the correct formula. So if anyone knows of where I can look to find such a formula, I'm happy to do the number cruching. Thanks in advance.
Closed Loop Plumbing Question
- Thread starter c_stowers
- Start date
DMBillies
Active member
If you're looking for a scientific answer to the question, I don't have one. However, depending on how you're setting up the the return part of the closed loop, the answer might be different.
In other words, my suction side is a piece of PVC maybe 12" long with hundreds of holes drilled in it. As such, no one hole has that much suction and the top set of holes could be placed pretty close to the surface (although mine is pulling from about 4-5" below). If the water ever got below the top holes, I would think the pump would pull enough air that the tank couldn't continue to drain (which seems to be a major concern of yours). If you're just planing on putting a strainer cap on the end of the pipe, you might have to go a little deeper.
If you do number crunch this, I'd love to see the answer, because it seems like there are too many variables you can't easily measure to be able to calculate it with any real certainty... that's not a challenge and I'm not doubting you, I'm just saying I would be uber impressed if your calculated answer reflected the actually reality.
With my math skills, it would be a lot quicker to just get an input that looks like what you want to use and fire the pump up in a tub of water to find out
In other words, my suction side is a piece of PVC maybe 12" long with hundreds of holes drilled in it. As such, no one hole has that much suction and the top set of holes could be placed pretty close to the surface (although mine is pulling from about 4-5" below). If the water ever got below the top holes, I would think the pump would pull enough air that the tank couldn't continue to drain (which seems to be a major concern of yours). If you're just planing on putting a strainer cap on the end of the pipe, you might have to go a little deeper.
If you do number crunch this, I'd love to see the answer, because it seems like there are too many variables you can't easily measure to be able to calculate it with any real certainty... that's not a challenge and I'm not doubting you, I'm just saying I would be uber impressed if your calculated answer reflected the actually reality.
With my math skills, it would be a lot quicker to just get an input that looks like what you want to use and fire the pump up in a tub of water to find out
I do plan on using a strainer on the end of some 2" PVC. However, your hole method is a good idea. I could drill a safety hole an inch or so below the water to break the siphon in the case of a major plumbing leak. In the worst case, if they hole becomes a problem (pulls a vortex and causes cavitation), I could always plug it with some epoxy and drill a little lower.
Pickupman66
New member
Chris, I use the same 12" pipe with the holed drilled in it. this way if I fish got too close, it would not get sucked to the inlet. when I first installed it, the first hole was about 2" form water surface and believe it or not, I got a vortex off that. so, I have about the depth of a 1" coupler lengthwise then about 4" to my holes. my outlets are about 2.5" deep to their tops. since I Have to go that far anyways for the siphon break. my best advice is make sure you glue the living tar out of it to make sure you have no leaks. mine has been leakfree since i installed it a week ago. I have noticed I can take off the inner pipe and clean it without the pump creating a vortex.
