it syphons back because the opening at the sump pump end is lower then the opening at the other end. work the same as a syphon
I suggest you install an anti syphon check valve at the pump which will prevent the water from running backwards.
you can also add a SMALL hole to the pipe at the highest point after the check valve to allow air to enter and let the water slowly drain out of the pipe when the pump shuts off so it is less likely to freeze.
Yes some water will come out of the small hole when the pump is running.
I have a curtain drain in the yard that runs into a 5 ft deep cement box with a sump pump in it. The 1.5 PVC pipe that was connected to it ran about 150ft. to a ditch and did not have a continuous drop, it went up and down causing a lot of water to run back into the sump pump box and hold water in the pipe also it made the pump run more often.
I replaced the PVC pipe with 3in. pipe and had a very slight drop to it as the 150ft. run does not have a lot of drop. I am still getting water coming back to the box/ sump when it stops again causing the pump to rum more often than it should. I know for sure my 3in. pipe is put in much better than the 1.5 pipe but still get close to the same water running back.
The sump pump has the 1.5 pipe lifting about 5 ft. as it comes out of the box and about 1 ft. past that is were I changed it over to the 3 in. pipe, could this be part of the problem? It seems the pump has to run 2 times before I see water coming out the end of the 150ft.run. I went back and checked the level of the 3in. pipe to make sure it has a drop going the right way. Part of the run it just level no drop but at no time is it running back toward the sump pump. I only had about 4 to
5in in drop for the 150ft run, that is why some of the pipe is set to level so I could come out from under the ground to daylight at the end of the run. I am thinking now that maybe I should have run the 1.5in pipe 10 or so more ft. before going to the 3in. pipe to give it more push. A friend thinks it's just the water causing flow back from the water hitting it's self and pushing it back to the pump.
I have not use a check valve because it get well below freezing here and I am thinking that if I put a 3in. check valve at the beginning of the horizontal 3in. pipe and it's not flow back it will fill the back part of the pipe and freeze.
Any ideas on why the water is going the wrong way? As I said no place in the pipe is it running back, the pipe is running with a drop or at least level, the level part being about half way in the run but the first and last part of the pipe run are on a drop.
If I add a anti siphon check valve the water above the valve will freeze as it would be vertical and hold water above the valve, the hole after the valve would drain but not above it. I wish this would work as that would fix it but unless I am missing something I will still have a freezing problem. But I understand the siphon part, that was one reason I went to the 3in. pipe, I was hoping it would have air above the water being a larger pipe and stop it from siphoning. I guess I could do the check valve and use heat tape in the winter.
The sump hole is about 5ft. deep and 36in. square, it's kind of big. The curtain drain pipe comes in at the bottom and the pump sits on the bottom. It looks like after the pump shuts off the water that runs back raises the level by about 2 inches, I have no idea how many gallons of water 2 inch rise is in a 36x36 square box is, but it gets close to setting the pump off again, if I add about 3 gallons of water it comes back on.
I know the water is running up hill to get back to the sump hole, so part of it must be a suction. I drilled a 1/8 hole in the PVC in the sump pit thinking it would stop the siphon suction but it still runs back in. Odd that it can run up hill back to the pit. I read in the groups looking up on why this can happen and seen someone say only a farmer can make water run up hill, I'm not a farmer but somehow I have water running up hill???
I thought your freezing issue was only outside... is it also freezing at the pit where the pump is?
when the pump shuts off, there will always be some water left in the pipe.
you have to decide what you want that water to do
if you do nothing it will all quickly run back into the pit becuase the low water pulls the water up hill this really isn't so bad si maybe just don't worry about it
if you add an antsyphon check valve, the water will sit in the pipe
if you add an antisyphon check valve and a small hole, the water will sit in the pipe but will slowly drain
you can use two holes. one hole in the pit just above the anti syphon value, then the water will slowly drain into the pit, maybe slow enough that it does't matter. you can also add a hole at the high point of the pipe (to break the vacumm) so some of the water can slowly drain out the far end.
But remember, a small stream of water will squirt out of the small holes when the pump is running.
and the water doesn't really run uphill, the opening at the pump is lower then the opening at the far end so the water runs uphill pat of the way but then runs down hill at the pump more then it went uphill. There is a net downhill for the water.
Thats another solution for you, if you can get the opening at the far end of the pipe to be lower then the opening at the pump, the water will continue to run out all by itself when the pump shuts off.
The water in a 3 foot x 3 foot pit 2 inches high is about 11 gallons. That is how much water is running back. Instead of a small hole at the top of the pipe, tap a hole and install a vacuum breaker, or an upside down u-shaped pipe with a check valve at the end which will act the same way. The pressure from the pump will push the vacuum breaker closed, then when the pump shuts off the vacuum from the siphon will pull it open. No water will come out where you don't want it to, and the siphon will be stopped.
I never had it freeze at the pump, but was worried it would with a check valve. It was the roller coaster 1.5in pipe that would freeze at places in the 150ft run and the water it was sucking back to the pump is why I ran the 3in pipe. I am guessing the pipe would freeze in the sump pit as it to, is outside going to a curtain drain fro water run off before it gets to my leach lines. I may give your idea a try on the anti siphon with the hole to release the vacuum.
Other posters mentioned anti-siphon valves, but they seemed to misunderstand how they work, thinking that they were check valves. An anti-siphon valve is effectively a check valve, but instead of being inline (to prevent backflow), one end (the "goesinto end" ;-) is in free air. So if you draw vacuum, the valve opens and lets air in.
Then it's not an anti-siphon valve, it's a check valve.
Sure it will prevent backflow (or at least MOST of the backflow).
If, as others surmise, the backflow into the pit is because the pit is lower than the outflow, and it's siphoning back, a valve as I describe (at the highest point in the line) will instantly kill the siphoning action and let the water drain out in both directions.
If there's risk of freezing in the pit, the anti-siphon valve will ensure that as little water as possible remains in the line.
If you use a checkvalve, then you guarantee that the line remains full of water even if the pit is dry. Which is a recipe for (eventual) disaster if the pit ever freezes.
In order to minimize the amount of backflow into the pit, and at the same time make sure that the lines empty when the pump isn't operating, you arrange things so that the high point of the line (and thus the position of the anti-siphon valve) is as close as possible to the pit.
In other words, run the line straight up from the pit to a height higher than any other in the routing to the outfall, and install the anti-siphon there. When the pump stops, then, you'll at most get a couple feet worth of line draining back into the pit - instead of siphoning back the whole line (or worse, that plus the contents of the ditch) into the pit.
I won't get to this till May 2, But I will post back what worked. I will try them all till I get it. I do think it will get it working without flow back, well I hope it does!! Thanks to all that gave me the things to try, I DO appreciate it very much.
So that the outlet pipe goes UP a wasys before going over. Don't know if that will help. But it makes sense. The other thought, is that if you can run a pipe way up (fifteen feet or so) you can put a vertical vent. Half inch or so. That way, you will not get siphon effect drawing the water back to the sump pump.
The inverted trap-like section of pipe will NOT prevent siphoning.
There, satisfied? ;-0
If you put a vent (or anti-siphon) valve on the pipe at the high point, it will prevent siphoning.
No need to go up 15 feet per-se, just go up enough to be higher than anywhere else on the line by a few inches.
It boils down to something like this:
- If the outlet is lower than the pit, you really don't need a check valve or anti-siphon. The water will simply flow out by itself.
- If the outlet is a bit higher than the pit, but lower than your head-room, you can use an anti-siphon valve. You can still use a checkvalve if you wish, but this would be bad if the pit is subject to freezing.
- If the outlet is much higher than the pit, you need a check valve, and an anti-siphon won't help. If freezing is possible, you have a considerably harder thing to solve.
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.