SPRINKLER TALK FORUM - You Got Questions, We've Got Answers

Is it not possible to grade a swale into the lawn?

Given that a French Drain is basically just a trench back-filled with rock to catch and divert flowing water.

A sprinkler system delivers water to the ground such that the water absorbs into the ground (i.e. you don't want run-off).

I don't see anything that would prevent you from running a French Drain ACROSS a sprinkler system, not to mention parallel to it. The only thing you would have to watch out for is making sure you don't damage the irrigation system during the construction of the French Drain.

HOWEVER, if you were to run a French Drain ACROSS a sprinkler system pipe (or any water supply pipe), you would want to find a way to sleve the water pipe from the French Drain backfill. The reason is that the backfill will be rock, and water pipes actually move/shift as water gets turned on and off. Over time, the pipe will deteriate from rubbing against the rock.

As an example, I live in an area with pretty rocky ground. It's common around here for the water supply lines between the water meter at the curb and the outside of the house to be 1" PVC (usually transitions to 3/4" copper just before entering the house). There is a house near me that the constractor simply backfilled the water supply line trench with the rock-filled-dirt that was dug out of the trench without any sort of a sleve or sand bed. In 10 years, this supply line has had to be repaired three times where deteriation of the pipe from rubbing against rock have caused leaks.

Do you know FOR SURE (i.e. you were there when the system was installed) where the pipes for the heads along the patio are located?

If you don't, there is the possibility that the main pipe is running parallel to the patio out in the middle of the yard somewhere with individual pipes running from the main to the head perpendicular to the patio. If that were the case, and you were going to do the digging with a trencher, you would want to dig between the heads and the patio so you don't risk running over the pipes.

Of course generally speaking, if you don't know FOR SURE where the pipes are, they could be ANYWHERE. Perhaps they are already in a trench along the patio with swing joints (or funny pipe) from the pipe along the patio to the heads. If you were going to use a trencher, now you want to be past the heads to avoid hitting the pipes.

And like you've said, if you don't mind the extra work, you can obviously dig a wider trench and locate/relocate the drain and the heads all at once.

Of course another attitude is to simply get a trencher and start digging where ever you want to place the drain... irrigation system be dam... just let the trencher rip it up as you encounter any of it, and as you backfill the trench, make repairs to the irrigation system, sleveing any pipe that is now located inside the French Drain rock. (This of course assumes you'll called the line location companies to know there are no utilities where you're about to dig).