My plan for my big sump is, for the flow to the sump filter screen on the bottom of the tank with a hole in the tube so if the water goes below the hole it will lose suction. As for the sump return. I rigged up a toilet tank float to a switch that will turn off the pump when the water gets to low. And when the water level gets to high the same switch will turn it on again.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-comfficeffice" /><o></o> <o></o> Also this is on a rubber made 100 gallon sump in another room
I was thinking of putting in a piece of plastic that the water would have to spill over to get to the return pump. If water wasn't being returned to the sump via the overflow then I couldn't overflow the main tank. The issue that would result is a burned up mag 5 or 7 pump. Is this feasable?
What kind of overflow are you using?
It should not loose the siphon.
I've been using a hang on overflow for 7 years and have never lost a siphon. I think you will find yourself covering up the problem instead of fixing it.
Find out why you are loosing the siphon and fix that.
I guess I should explain. I do not have my tank and sump set up. Many people advise against using a hob overflow. They suggest drilling the tank. I really have little desire to drill my tank. I was looking for ways to prevent a main tank overflow incase of siphon loss.
Those overflows should have a divider that extends up about half the height of the box for the outside section of the overflow. The half that has no drain in it is the side you put the outside half of the U-tube into. The water from inside the tank must fill this chamber, and overflow the divider in the outside half of the overflow in order to go down the drain line to the sump. The inside box will only drain as low as the bottom of the gaps for the strainer teeth, even if the water level inside the tank were somehow able to continue to drain (which it cannot unless there is either a leak or another overflow that is lower than this one). When the level inside the tank drains down to the level of the strainer teeth, no more water will drain out of the tank, and the siphon will stop flowing, but not break. The water will drain through the U-tube into the outerbox, but will stop draining when the inside stops draining, AND THE WATER HELD BEHIND THE DIVIDER WILL NOT BE ABLE TO FLOW DOWN THE HOLE IN THE BOTTOM OF THE EXTERNAL HALF OF THE OVERFLOW. This maintains the siphon until power is resuplied to the unit by keeping both ends of the U-tube submerged under water in the overflow boxes. Unless there is a leak of some sork, or if the water stops for so long that it evaportes to expose the ends of the siphon tube, then the siphon will not break.
--Snail crawls into the siphon tube and occludes it
--Algae is not cleaned from tank or overflows or siphon tube and occludes the siphon tube
--siphon tube is too small or box is inappropriately sized (from the start, or a larger pump is added) and begins to collect air due to rapid turnover of water into the internal skimmer box, leading loss of siphon once enough air collects at top of siphon.
--Dead (fish, crab, seacucumber, macroalgae, etc.) somehow makes it past the skimming teeth in the internal box and occludes the siphon tube.
All these are avoidable, but potential problems for the overflow siphon tubes, but most of these are also possible with the drilled tank overflows as well.
I meant to add that I kept these types of overflows for MANY years until drilled tanks became popular, and I never had an issue with them. I did find that using 1&1/2" PVC and a piece or two from a P-trap makes a really good large volume siphon tube when placed in a deep overflow box on both sides (with the divider in the external box extended up at least high enough to prevent loss of the internal box siphon) was just about idiotproof. The most difficult thing was threading the air line inside the siphon to suck out all the air.
OK. I thank all of you for your answers. My original question though still stands. Is there a way to starve the return pump of water if some catastrophe happens that makes the overflow stop working as planned so that I can avoid a main tank flood.
I don't know what you can do?
One problem is that the area where your pump is, is where the evaporation shows up.
In other words if your tank evaporats 1 gal per day then that area would need to be able to handle that loss and be large enough to handle the drainage from the tank when the pump isn't running.