In my quest to plumb the backwash from my pool, this is what I need. A valve of sorts that will do the following, when the line is under pressure, (while the system is backwashing) the valve will be forced closed, but when the system is off, the valve will open allowing the residual water left in the line to drain out to a small drywell. A simple visual is as follows, obviously the pipe will be buried with a slight grade from each end so the water will flow to this "valve". I am think something along the lines of how a thermostat works with heat( opening and closing) but with pressure as the variable. I know I could just use a ball valve and do it manually, but I would like to bury this and have it do it automatically. This is all done in 2" PVC.
A brass check valve with a "swinging gate" could be angled slightly upward so that the gate opens slightly when the pressure is off might do it. Or, just have a small hole at the end of the pipe that will drain it gradually, but not much water would get through during the backwash cycle.
To develop/alter your idea a bit - build a vacuum breaker:
1) Have the drain pipe slope downwards away from the pump. No low spot in the middle as the OP suggested. No drywell required.
2) Install a T fitting on the outlet of the pump. The pump is one "wing" of the T, the center part is pointing down and connects to the drain line. The other "wing" of the T is a swinging gate checkvalve (horizontal, or pointing slightly down - hinge on gate on _upper_ side).
This can be all done with plastic components - whole system for less than the cost of a 2" brass check valve. You _should_ be able to find a suitable checkvalve in a place that caters to sump pumps.
When the pump fires, the gate will slam shut, forcing the water down the drain. When the pump stops, the vacuum in the drain will suck the gate open, and the water in the drain will run/siphon out.
The checkvalve may "blort" a little during activation. If enough to be annoying, elastic band a sock to the outboard end.
My system is somewhat similar to this. But instead of a T I have a two-way valve, and instead of the checkvalve, I have a fitting that connects to a 2" firehose.
When backwashing, I direct the valve down the buried drain line. When I stop backwashing, I direct the valve to connect the drain line to the hose connection. The hose is sufficiently porous that it will allow enough air in to let the drain line empty quite quickly.
And if I have a fire (or just a rambunctious teenager ;-), I run the pump straight to the firehose...
A good PVC 2-way valve will set you back about $45 CDN ($30-35US). My pool supply place ordered one in for me.
Short lengths of 1/2" PVC conduit drilled into a 2x4 make a great way to hang firehose.
[For some strange reason, the previous owners of the house left three
50' lengths of 2" real canvas firehose. I _think_ they were using them for irrigation. Got a decent nozzle from a flea market. My "fire control" system ended up costing about $50 in total.]
Not sure if I want to try the brass check valve, I had thought about just plumbing from a T to with and end cap that has maybe a 1/4 inch hole drilled in the end. Just letting what water does escape thought it during the cycle escape, it would then just function as a drain when the pressure was off.
I have some other ideas that I will add in the next reply.
The point of the drywell is to have zero water to contend with at anytime. Water will be visible of course while the system is backwashing, the water will be launching from my estimate, about 35 feet at about a 60 degree angle from the "head" I fabricated, over the back wall into a greenspace. From my latest test the water streams(two 1 inchers) reach a height sufficient enough to disperse into non eroding droplets.
I am trying to make the whole system work with no other effort than changing the setting on the filter valve. It is not that I am lazy and don't want to move hoses or the like, I just want as little of this visible as I can get., including having no draining water visible anywhere. To clarify I will attempt another diagram of the current flow : )
The "head" that I made sits just below the top of the inside of the wall and "fires" the water at a height and angle
into the greenspace.............................................. about here. It is pretty cool to see that aspect of the cycle.
The key here is that the water during the backwash cycle will travel about
25 feet at ground level then up the back wall about 6 feet to the head where it will be expelled. When I turn off the backwash cycle, there will be 31 feet of 2" pvc with water in it that needs to go somewhere, hence the valve and drywell idea.
I think I have figured out how to create a valve that will shut when pressurized and open when not. Hard to explain, but it has to do with a ping pong ball within a 4 inch chamber. There will be a hole at the end of the chamber( on the inside) that will have a "seat" for the ball. When pressurized, the ball will be pushed into that seat sealing the hole. ( if it leaks a little no big deal), but when the pressure is off, the ball will"float" away from the hole, allowing water to drain. I need to find a suitable "ball" that will resist and residual chemicals, but will also be buoyant. The chamber will just be a 1 foot length of 4 in PVC a 4 - 2 reducer on one end to connect to the T in the main line. The other end of the chamber will have a screw cap with a hole in it, the"seat" for the ball will be honed into the inside. I might try to add an O-ring somehow.
I can certainly sympathize with not wishing to drag lines around. That's why I replaced the drainage system (originally just a chunk of firehose) with a buried line. But I have a downslope...
My proposal would work to do exactly what you want, provided that you could establish a downslope to the ejectors. Essentially what happens is that when the pump shuts off (or you switch the flow away from the drain), the checkvalve would open letting air in, thus the remaining water in the line would dribble out thru the ejectors (quite quickly in fact). Further, all the "active" components are above ground and easy to inspect.
I take it then, that the ejectors are at about the same level or higher than the pump. Even if the ejectors are below the pump, if there's a big rise from the pump getting there, at 2", suction will _not_ empty the line.
This leads back to your original idea of having some sort of valve at the low point, that is closed only when under pressure from the pump. Or, a manual valve. Or, a simple restricted flow orifice. Whichever you've chosen going into a drywell.
Issue: a restricted flow orifice (ie: a 1/4" pinhole) will be subject to clogging. Especially buried, this could be quite a nuisance.
Issue: a valve of this type (a spring-loaded checkvalve) may be difficult to obtain. You want it to open when the pressure is below, say, 1.2 times the head of the lines. Ie: if the head is 6 feet, you want the thing to open anywhere below 9' (5 or 6 PSI).
Issue: the checkvalve may also be subject to clogging - a real nuisance if you have to bury it.
At this point, my recommendation would be to see if you can establish the low point really near the pump, and install a manual valve running thru hose to a drywell, or a garden, or .... Ie: a ball valve. Even a 3/4" one would do.
Hold a second. Irrigation systems (eg: pop-up sprinklers) often have little drains that you can install on the bottom of the heads. _Maybe_ these will do it, even tho it's only going to be 1/2" or 3/4" in diameter. I've not seen these at retail outlets (eg: HD) nor used one myself, but perhaps irrigation installation companies do.
[I'm not sure how reliable these will be in _completely_ draining the line. They should be very cheap tho, so install a couple ;-)]
Either that, or consider installing a water feature...
If you're subject to freezing in your area, while 2" PVC will stand up to considerable abuse in this way, you're going to have to try hard to ensure it drains completely at least once in the fall. Blowing a 2" line will be extremely difficult if not impossible short of hiring someone with _big_ equipment.
I personally wouldn't mind the water staying in the line. I'd disconnect the line at the low point (hopefully very near the pump) to drain it in the fall.
Chris, i do appreciate your input, very informative.
I think this may be key here. I am in Arizona just outside of Phoenix, freezing really is not an issue, thought it did drop to 24 degrees 2 consecutive nights last week. Being from the Midwest originally, I think that is where the idea of having to drain the line came from, kind of a conditioned response I guess. I don't think a draining the line is necessary for this area. The water can just sit in the line. I will install a manual valve near the pump just for utility sake. ( I still think my ball in a chamber idea would function well enough with some trials : ) Thanks for the perspective, you saved me some work !
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