Looking for a valve to stop backflow from a dry well

[BobA]

Hi,

The short version is this: I'm looking for a valve that allows outflow from a water softener into a dry well, but will block a high water table from flowing back from the dry well.

The long version is this: I have a water filtration system (softener, acid neutralizer, and rust remover). They all regenerate and drain their backwash into a dry well. But when the water table is high, the backwash backs up into the house and spills onto the floor.

So my idea is to put a T in the pipe that goes to the dry well. Have that T go up, against gravity, and then feed into the septic system's holding tank which is just a few feet away (not into the septic tank itself). So backwash will normally go to the dry well, but when the water table is high and the dry well is full, the backwash will go up the T and flow into the holding tank, where it'll get pumped up to the drain field.

The one problem is that if the water table goes above the T, ground water will flow from the dry well into the holding tank and my pump will be trying to drain the entire yard. So I want a valve between the T and dry well. When the water table is low, backwash will be able to flow through the valve and into the dry well. When the water table is high, ground water will come into the dry well and flow back through the pipe, but the valve will be pushed closed and the ground water won't flow into the holding tank.

I've discussed this with my septic guy and he says it sounds good in theory but he has his doubts that it will work in practice. He can't really specify what he thinks will go wrong, but he's skeptical. And so I turn to the folks here.

Is there a valve on the market that would work here? Is there any reason to doubt it would work?

Thank you,
Bob

 

[Reach4]

How about putting an elbow on the pipe going to the dry well, and put a no-trap standpipe feeding the elbow? Water treatment drain lines would feed into the standpipe.

If this does not fit your current setup, try posting a sketch that illustrates the current path from your water treatment drain lines to the dry well.

 

[Sponsor]

 

[BobA]

I'm not sure what you're suggesting with the standpipe and how it would help. The problem is that when the water table is high, the dry well is already full of water. When the water softener regenerates and dumps the backwash into an already-full dry well, the backwash just spills into the house.

If the water table is low, everything works fine.

I hope the attached picture will clarify things.

- Bob

 

[Reach4]

That clarifies. I suspect the backwash is not via a pipe, but via a leakage path. Are you thinking otherwise?

 

[BobA]

Again, I'm not sure what you mean (I'm not a plumber so I don't know all the terminology). There's a PVC pipe inside the house that receives the regenerating backwash from the water softener and takes it out to the dry well. But the PVC pipe is not sealed inside the house; it's open to the air. So if water backs up in the pipe, it can spill out that opening.

- Bob

 

[Bannerman]

Not clear on how the water is 'spilling' into the house. Is the spill from one of the drain lines connected to the softener or filter or is there a leak into the house from outside? (I now see your explanation in post #5).

If the dry well is full due to a high water table, what then occurs with the septic drain field? Does it also flow back into the 'holding tank' and then ultimately back into the septic tank?

To answer your question, if water is flowing backwards through a pipe, I suspect a common check valve (backflow preventer) would eliminate that situation.

If the drain field is also backing up, I suspect the 'T' will not help. You may wish to consider a sump for the water treatment devices to flow into, and a sump pump to pump out the sump into either the septic tank as it should be, or discharge a distance away from the house.

 

[Reach4]

Again, I'm not sure what you mean (I'm not a plumber so I don't know all the terminology). There's a PVC pipe inside the house that receives the regenerating backwash from the water softener and takes it out to the dry well. But the PVC pipe is not sealed inside the house; it's open to the air. So if water backs up in the pipe, it can spill out that opening.

Where on your sketch is the spill-out point?

The red on img_5.png is the standpipe I was proposing.

If water comes in around the pipe, that would not help. Also, in high water conditions, water would come out of the ground outside.

So I understand the advantage of the two-destination objective. Suppose in your proposal, there was no check valve. If the water rose high enough, the water would cross over into the holding tank.

If that holding tank is going to your septic system, you would need a trap to keep gasses from coming back from the septic system.

 

[BobA]

Hopefully the attached drawing will clarify how the water is spilling out.

The drain field is on a hill and the holding tank has a pump that pumps water up to it. So the water table isn't an issue for the drain field.

I googled for a "check valve" (that you for providing the terminology) and it looks like it's for vertical supply lines, not horizontal drain lines. Following other hits, I came across "flap valve" which, if there's one available for the size pipe I'm dealing with, might be the answer. But I've also seen that it doesn't form a tight seal and maybe that's why my septic guy is skeptical.

- Bob

 

[Reach4]

The drain field is on a hill and the holding tank has a pump that pumps water up to it. So the water table isn't an issue for the drain field.

So that is an existing part of your sewage system. You need a trap for any line going into that.

In my diagram, imagine it is like your latest, but with the vertical pipe extended significantly higher.

I googled for a "check valve" (that you for providing the terminology) and it looks like it's for vertical supply lines, not horizontal drain lines.

The ones with a ball and a spring can be at any orientation.

 

[BobA]

I hadn't thought about needing a trap, but that makes sense. Thanks.

I googled some more using some of the terminology you've provided and came across a "backwater valve". That looks like what I need.

- Bob