How much water left over backflow valve?
I live in Zone 4 (freezing winters).
The outlet from my sump pump comes out of my house about 6 inches above the ground and dives immediatedly down into a buried tank in the back yard. This tank is nowhere near large enough to handle some of the recent rains, especially while the ground around it is frozen. Sump pump pumps out, water flows right back in. Sump pump runs continuously, electrical outlet ‘resets’. Pump stops, water floods the basement…
I want to run a PVC pipe around from the back of the house where the outlet is currently to the front where the property slopes down to the town’s storm sewer system in the street. In order to get a 1/4″/foot slope to the pipe I have to start it about 28-30″, about 24″ above the current location of the outlet, at the back of the house. This would mean a riser of about 24″ from the current location of the outlet exposed to often freezing temps.
My question is do I have to worry about water remaining in the riser section outside the house freezing? How much water remains in the pipe after the sump turns off? Is the whole vertical length above the backflow valve full of water?
Could I run my sump pump’s pipe straight up; from above the check valve straight up, and then at a slight upward slope across to the outside wall, and then put in a T-fitting (actually, probably a Y-fitting) at the very top of this upwardly sloping section by the sill plate with a 1/2″ “drain” pipe leading back down to the pit? That would leave water in the main pipe above the check valve but allow for the water in the outside vertical section to drain back. Any issues with this idea? Would some of the water pumped out by the sump end up draining back into the pit during the pumping process? If I mounted the Y-fitting so that the “drain” leg was above the main pipe angled slightly upward but still below the base of the outside riser section, would that help? Are there one-way self-actuating valves that based on water pressure flow only one way. When the pump is going it would close off the “drain” leg but then when the riser was trying to drain back would open (though I think the pump would be exerting pressure up the drain segment as well)?
Am I worrying about trivia, overthinking the “problem”? Creating an issue where none exists?
Thanks for any input
Edited 3/9/2009 5:47 pm ET by QuestionsIhaveQuestions
Replies
No one knows how much water is left over a check valve?
How about this: can I run a small drainback line back from the sill plate area of the discharge pipe to UNDER the check valve? Something like an IAC on an efi throttle body? Would I have venting issues if the drainback pipe was essentially open to the atmosphere after the water in the riser section drained back into the pit through the pump?
Well, there is definitely some amount of drain back because you can hear it and on top of that, the water draining back is what closes to backflow valve.
To quote a commercial, "you're not thinking with your dipstick, jimmY" grab a fishtape and mark it off every foot for a couple of feet and feed it in one foot at a time (and pull it back out) until you find the water level.
Unless the check valve doesn't seal, all the water between it and the beginning of the downward slope will remain in the pipe.
If your sump pump oulet is 2" diameter, and the section of vertical pipe above it is 10 feet, the pipe will contain 1.6 gallons.
Obviously, the higher the checkvalve is on the inside, the less water will be retained above it.
Could you remove the checkvalve and just allow the 1.6 gallons to flow back into the sump? If the sump has, say a 5-gal capacity before cycling on, this could work.
To reduce the backflow from the riser, suppose you used an 1-1/4" discharge pipe? The retained water would then be only 0.64 gallons on a 10-foot riser. At the point where the water begins to flow by gravity, you would want a pipe large enough (2"?) to handle the pumped flow by gravity flow. A 1-1/2 " riser would retain 0.9 gallons.
Why not just drill a 3/32 hole in the discharge pipe inside your sump? This way the water drains into the sump leaving the pipe free of water.
That small amount of water being pushed out during the pumping cycle is not going to amount to pee.
Of course you could also drill this hole anywhere along the riser from the sump to the maximum elevation and just let it flow thru tubing back into the sump.
Get it?
It's commonly done to eliminate starting head pressure.
i've been confused by the thread and the Q - I have four sumps for on the job use. Three different brands. And I used to check on a lot of houses thru the winter.Never had one with a check valve. Always half a gallon to a gallon flow back down.
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There is a check valve that "can" be installed. It prevents all the water that is trapped in the line from draining back into the sump pit.
Nobody ever said that it had to be installed "close" to the pump.
Did that help?
You also can't install a vent at the high point. The water will be pissing out of it when the pump is running. You're not dealing with a siphon but who cares if you are? You're trying to get water out of point A and flowing into point B.
What I don't understand is the use of the cistern
Without the vent it'll siphon back out of the cistern -- precisely the problem he's having. Whether the vent will "spew" or not depends on how much head is generated and how high the vent pipe runs. Besides which, you WANT the vent to overflow when the cistern (dry well) becomes waterlogged.
The modern conservative is engaged in one of man's oldest exercises in moral philosophy; that is, the search for a superior moral justification for selfishness. -John Kenneth Galbraith
I didn't read into that. If that's the case just shorten the pipe entering the cistern, cut off anything lower than the roof of the tank. On top of that he wants to discontinue the use of the cistern as it does not have the volume available and is asking about getting the water out of the line so it will not freeze.
Perhaps I missed something.
Edited 3/14/2009 11:42 am ET by RobWes
Thanks for the replies.A little more detail:There is a plastic tank buried in the back yard to meet some village code about not sending rain water into the storm sewer system and not flooding the back yard??? I don't understand how the second part can be avoided if the tank out back has an overflow vent sticking up into the yard, but...The buried tank just isn't big enough, the water during a heavy rain just bubbles out of it, sinks back into the ground and I think is just following the buried pipe that leads to the tank from the home's sump pit back to the house and then down to the footing drains. It's pretty immediate the flow back into the sump pump if the pump's plug is pulled while it's pumping. Or is that just built-up pressure in the outlet line to the full tank? Whatever. I just want to reroute the sump's outlet line to run around the house to the front yard where the ground slopes clear down to the street. The tank can stay buried and unused as far as I'm concerned.The outlet pipe is 1.25" PVC with the check valve mounted about 3' above the pit's cover. I thought it was required by code, but do I really need it? Not having it hold the water up after the pump shuts off would take care of the issue. Also, this pit rarely pumps during the winter, if there was some reason for the check valve; could I just bypass it during the freezing months?Thanks again for the opinions.
There's no good reason for the check valve if you will be abandoning the tank.
Check valves on sump pumps are there primarily to keep the sewage in the discharge vertical pipe from dumping on you when work on the pump, and to prevent any backup from the sewer line from flowing back into your house. You have neither problem since you're not pumping sewage and since the discharge is not connected to a sewer that could back up into your house.
You don't have to worry about siphoning the backyard tank back because you mention that there is a vent on the tank--that vent will effectively break any siphoning action even when the tank is full, so the check valve serves no purpose in preventing siphoning.
If you abandon the tank, everything is easy: disconnect from the tank, run the new pipe, remove the check valve. In fact, you don't even have to remove the check valve in this scenario.
You could peserve the use of the tank if you want, or if you believe it is required, and still provide for effective discharge of the overflow. Install a tee on horizontal portion of the discharge pipe where it leaves the house on its way to the tank. Orient the tee so that the branch is pointing straight up, and run the vertical pipe from the tee branch up to the height you need to get the slope required to run around to the front of the house. The discharge will flow thru the straight run of the tee easier than climbing up the tee branch until the tank fills.
The vent on the tank will need to be raised up higher than than the point where the new around-the-house pipe turns horizontal--otherwise, when the tank gets full, the excess water will flow out the vent pipe instead of flowing thru the tee that directs the flow to the around-the-house pipe. How much higher? Probably only 6-12" if the tee branch pipe is 2" pipe, and the discharge to the tank is 1-1/4".
Thanks. Very helpful.Another question: is there something like a t-valve (pressure-activated) check-valve? When a backup occurs, pressure backs up (from the tank pipe for example), the valve will flip open to another pipe?Or is there an outdoor valve that will work in freezing temps that I could install to manually redirect the sump output from the tank to the outlet pipe? I suppose I could drill two outlets through the sill with a manual valve inside controlling which pipe gets the discharge...Thanks again.
First, let me say, disregard the part in my last post about not needing to remove the check valve. I momentarily forgot your point about freezing danger--that was why you had the original question about how much water would be left above it.
I am not aware of the kind of two-way check valve you are wondering about. Besides which, I have an inherent distrust of complex things. All you really need to accomplish, if you want to retain use of the yard tank, is to find a way to encourage the flow to fill the tank first, and when it's full, to start the water flowing in the around-the house pipe. That's the reason for my suggestion to use the tee with the flow to the tank on the straight-thru run, and a larger branch that runs vertically up to where it turns horizontal. The vent for the tank must be higher than the point where the overflow (around-the-house) turns horizontal, so that the head of pressure that develops in the vent riser forces the flow into the overflow branch of the tee. You'll have to experiment with the height to determine just how high.
Your problem isn't drainback but siphoning. You need an air vent somewhere on the discharge side of the line, near it's highest elevation.
You could always put on a short section of heat tape.
Mike