Irrigation mainline crossing sewer line

a_lost_shadow · 05-05-2012, 04:58 PM

I'm in the process of installing a sprinkler system. In digging the trench for the mainline, I discovered that I need to cross my house's main sewer line. Unfortunately, the sewer line is only 18" deep at the top.

Even though a permit isn't required here for sprinklers, I'm assuming that the mainline has to, or at least should, follow the same code limitations as the building supply lines. The California plumbing code (609.2) requires that all water pipes crossing sewer pipes made of clay, or materials not approved for indoor use, have a separation of at least 12". Additionally, the pipes must be buried at least 12" under ground.

Thus I believe that I need to replace a 3' section of the clay pipe with PVC/ABS, which will allow me to run the pipes with 6" separation. From my research it seems the best method for connecting clay to PVC/ABS is the flexible connectors, such as the ones may by Fernco.

Not having dealt with DWV lines before, I wanted to check to see if this sounded correct/logical before I had it added to my current plumbing permit. Also, I was curious if there were any better ideas for the situation, and/or for connecting clay to plastic pipe.

Finally, the sewer line runs parallel to the sidewalk leading up to the house. With the edge of the sidewalk pretty much on top of the center of the pipe. Are there any good methods to support the sidewalk while the area around the pipe is excavated?

Thanks in advance.

**TheEplumber** · 05-05-2012, 05:48 PM

You're over thinking this. I don't think your plumbing code is addressing irrigation lines. And you would want to sleeve the water line instead of messing with the drain. Also, your irrigation line should have a backflow device that is code compliant so your potable water in the house is protected.

a_lost_shadow · 05-05-2012, 07:29 PM

Potentially over thinking this is one of the reasons that I asked about it. I have a bad habit of doing so.

I'm planning on using anti-siphon valves for backflow prevention, which protect the laterals but don't provide protection to the mainline. Thus the reason I started treating the mainline like a water supply pipe. I'll start looking at how much it'd cost to put additional backflow prevention to protect the mainline.

I'm already planning on putting the line in an IMC sleeve to under the sidewalk. With the rocks around here' I'd rather put the sleeve in case the line ever needs to be repaired/replaced. Would extending the sleeve through the stay out zone for the drain pipe be considered acceptable?

The other reason I was open to touching the drain line was due to a recommendation that I add an external cleanout for my main sewer line where it left the house.. The current cleanout is about 3 feet inside the back of the house and offset from the door to the crawl space.