Friday, July 12, 2024

Repairing the French Drain

 The camera had identified what appeared to be a root blocking the French drain, so it seems that it needed to be dug up and repaired. The guy who ran the camera used a device to locate where the camera was in the pipe and marked the spot on the surface, so I knew, more or less, where the break was.

The French drain should be running along parallel to the side of the lot, parallel to the fence,  so I started digging where that should be.

Luckily I missed the irrigation line.  About two feet down, I found the French drain.

The French drain consists of three 4-inch PVC pipes surrounded by rock wrapped in landscape cloth.

 Peeling off the landscape fabric exposes the rocks

And removing the rocks exposes the pipes.

Now we know that the blockage is somewhere around here, but it may be a bit up the pipe or down the pipe.  We can't really be sure.  But it seems we are just downstream from a joint of some kind, so we can replace the pipe at that joint.  So we cut into the pipe and then will check up and down to find our problem.

And the blockage is just at the joint.  But it is not a root; it's just a bunch of wet and decaying leaves.  Pulling these leaves and the ones downstream from our opening out by hand, we seem to clear the pipe.  Putting the camera in the pipe to see what is downstream from the opening, we find

The pipe is open, but there is an opening in the side of the pipe.  Cutting a larger section out of the pipe, we can see the opening clearly.

Something has eroded or chewed an opening in the side of the pipe and then into the adjoining pipe, or it came from the adjoining pipe and broke into the center pipe.  This does not seem to be from just erosion or corrosion. It looks more like something chewed its way from one pipe to the other.  Since the entire system is under ground, where did it come from and where did it go.  Actually, there is an entrance/exit from the roof, into the rain gutters, down the down spout into the drain pipes.  Something could have gotten in when the roof was replaced, and the gutters replaced.

There is an pointy edge of the pipe that sticks into the main drain line.  This could start collecting leaves and slowly clogged the line with leaves, which would have been washed down from the roof during the time when we did not have leaf guards over the rain gutters.

But to repair the line, we have to take it out and replace it.  We cut out the section that is damaged.

This presents us with another problem.  The line is supposed to be round, but the top has collapsed, and even the part of the pipe remaining is seriously compressed.

Looking into the pipe, it seems this is the case for some distance. 

This section of pipe should be 10 feet long, and then there is a joint for the next piece of pipe.  That joint should be more round, so we need to dig all the way to the next joint in hopes of getting a round pipe to attach our replacement pipe.

We first identify the area that we will need to trench.  Ten feet from the last joint to the presumed next one.

 One day of digging gets us down about 12 inches, making a trench that is 12 inches wide and 24 inches from the fence.

Another day of digging gets us down to the landscape fabric around the French drain, 20 to 24 inches deep.

Once we open up the landscape fabric and remove the rocks, we have the pipe itself.

And as we expected, the pipe was 10 feet long and slips into another pipe.

The joints are not cemented, so we can just lift the old pipe out.

This puts us in position to rebuild the French drain.  First we build a new clean-out and attach it to the pipe coming down the hill.

Then we need a new pipe to go from this new clean=out down to the other pipe.  We buy a new Schedule 40 heavy-duty PVC 4-inch pipe and trim it to about the 100 inches that are needed from the clean-out to the pipe at the other end of the trench.

This slips into the clean--out end just fine, and leaves us with two pipes that abut at the other end -- one the new Schedule 40 PVC and the other the flared end of the old drainage pipe. 


The flared end of the old drainage pipe is not quite round.  It is stronger than the pipe we removed, but it has still been squashed into somewhat of an oval.

However, just as a force down squashed the pipe and caused it to stick out on the sides, if we use a wedge between the pipe and the earth/pipes on both sides, we can squish it back in towards the center and up in the middle, getting it temporarily back to a more circular shape.  We have to dig out all around it, including below, so that we can attach something to the end of the old drain pipe.

Searching for what we can use to connect these two pipes, we note that both of them have an outside diameter of 4 inches.  Checking at Home Depot, we found a flexible rubber connector that works for two 4 inch pipes -- the Fernco 1056-44.  It slips over the joint and has two worm gear clamps to hold it tight to the pipes.

Since it is flexible rubber, it doesn't matter that the old drainage pipe is not quite a perfect circle.  We can slide it onto the Schedule 40 pipe, lower the pipe into position and then slide it back over the end of the old drainage pipe.  Then the two worm gear clamps can then be used to tighten it in place.

 That then finishes the repair and rebuilding of the drain itself.

We want the pipes to be well supported, so we put sand around them, to get a tight fit and complete support.


I know it looks like dirty water, but it is five 50-pound bags of sand ($30.15 from Home Depot).

We wet the sand down, to help it flow into any hidden spots, so that it supports the pipe, then covered the pipes with the rocks.

 Added a layer of landscape fabric.

 And then buried it all with dirt.

But, we used some of the dirt from the digging to even the back yard perimeter around the new fence that the neighbors at 10600 put in, so we need more dirt.  We bought 32 bags of the dirt we have been buying from Home Depot ($99.42) -- two trips with 16 bags each time.

Spreading the dirt around, fills the trench, and can be raked smooth.

Then we can turn our attention to the Blue Rock Pool, where the French drain terminates.

We use the rocks to slow any water flow and allow it to soak in, but we don't want the rocks blocking the pipes.  So we put a plastic cage around the end of the pipe, so that the water can freely flow out.

We bury all that under the plain river rock,

And restore the Blue River Rock on top of that to give a finished appearance.

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