We had our french drains reworked when they put in the pool, but I think they only put a 1-way on the pool overflow, to stop the drains from backing into the pool.
Our drains flow to the open ditch at the street, but the outlets are pretty low in the ditch, so when the water level rises in the ditch, we get slow drainage & backflow onto our patio.

The drain lines at the ditch & anywhere the pool project didn't rework with PVC, is corrugated pipe [either 3 or 4 inch, I'd have to double check].

I need a low pressure flow solution for an in-line backflow/check valve to keep the ditch from backflowing onto the patio, that I can tie in to corrugated pipe..

Down here we turn the pipes up 90 degrees and install a pop up valve, this allows a one way flow. Any major retailer like Hoe Desperate or Lowes, Ace should have something that will attach to the end of the pipe and prevent backflow.

Link

The problem with a check valve it would constantly get clogged.
The Frenchdrainman on YouTube has great videos on the subject and a web site for parts.

We had a 90* pop-up at our old house, but it exited at the curb
With how our drains are oriented, not sure a 90* pop-up would work well here.
Not sure that clogging would be a real issue either, as the patio drains have covers & the house gutters are almost all covered as well.

I have a section of the drain pipe to repair, crushed by the excavator during the pool dig & not noticed until the patio was done [and excluded via contract], so was thinking about putting the 1-way there, possibly adding a surface box/drain there as well & tying in a downspout that's roughly 90* from where I need to make the repair. Figure having one of the drain boxes would allow for cleanout of any debris that may accumulate there.

Thinking about this more
Plan is to find where the drain pipe is damaged, splice in a repair section of the corrugated pipe

Add a catch basin there as well, for drainage in that area, as it tends to hold a bit of water after heavy rain.

T off the repaired section to also tie in the corner downspout from the roof gutter, which should reduce standing water in that area.

Add the 1-way downstream from the catch basin, maybe at the downstream exit of the box to allow debris cleanout.

Challenge now is finding where the drain is crushed, I have a general idea where, but don't want to trench more of the yard [by hand with a shovel] than I have to.

Looking around, it looks like backwater valve is the term I'm looking for.

quote:

crushed by the excavator during the pool dig

Other than sending a scope up the line and using the cable to measure distance, then it's working your way through the pipe where the excavator was used.

You can buy the pop up cap by itself, wonder if it could be used on the end of the pipe you have without the 90.

quote:

Originally posted by P250UA5:
Looking around, it looks like backwater valve is the term I'm looking for.

backwater is usually sewer & on a smaller line than 4". I don't think I've ever seen a 4" corrugate check-valve & a quick internet search only finds 6" as the smallest field-tile usage. (agridrain.com, look around for ideas).

I don't think a check valve will do what you want to do. If it ever plugged up, you'd have far more trouble than it was ever worth. Water will flow from high to low & will find creative ways to get there. A pop-up in an area lower than your patio would do more but if your patio is the lowest area available, it's going to have water on it.

The exit of the system, at the ditch, is lower than all of the feed inlets in the system.
The issue is with a lot of rainfall, the water level in the ditch gets higher than the drain exit, and thus backs up the line/prevents draining.
With extreme rainfall, we've had the water level top the ditches & I don't want that backflowing to my back patio/pool.

I'm meeting with my pool guy today for 'pool school' & will see if he knows what kind of 1-way they put on the pool overflow.

I'm not trying to diss the OP. I'm just wondering out loud. If you have to worry about water backing up into your area doesn't that mean the French drain is somehow designed wrong? Because isn't the point of a French drain to drain water that's accumulating in your yard when it's raining? And if it's raining, then water where your drain is draining into is also accumulating and is liable to start backing up into your yard at exactly the same time you want the water in your yard to be draining outside.

I had a French drain install recently because the inspection report I got done before buying the house noted water was coming into the foundation crawl space.

But in addition to the French drain, we had the town / city dig the ditch around the house deeper. They get plenty of water around here during monsoon season.

And maybe the OP's French drain is designed the best it can be given the circusmstances.

Your last line is the case, I believe. We're in a fairly low lying area, but the house has never taken on water. Just trying to mitigate as much as I can, where possible.