I received estimates on getting an irrigation system installed in my back yard. The majority of the cost is for digging down to the house's line in the front of the house (4 feet deep), splitting the water line, adding a backflow preventer, tunneling under my walk, trenching all the way along the side of the house at a depth of 2 feet, and then installing a drip system.

Today I was in my basement looking a where my water main comes into the basement, and am curious if there's a reason why they can't just split off the main where it enters inside my basement, route the main along the ceiling of my basement, and then out into the backyard through the basement wall?

Is there a reason this is not a good idea? Would love to save the time/trouble of digging all those trenches if there's no serious downside to going through my basement.

  • Is the existing pipe going to be adequate to feed both the sprinklers and household use while maintaining adequate pressure? I've seen this done, but I believe they put in larger-than-usual pipe from the main to the house to make up for it. (And then installed two meters after the split, since in that town irrigation water isn't charged the portion of the bill which funds the sewer systems.)
    – keshlam
    Sep 18, 2014 at 3:07
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    I don't think it will be an issue, as the irrigation people's plan was to split my water line just outside the wall of the house, not run a line all the way from the city's main.
    – John
    Sep 18, 2014 at 3:10
  • In that case, I'd certainly ask them why your alternative wouldn't work. There may be a good reason, though I'm not thinking of one offhand. Then again, I'm better with electrical than water, and better with bytes than electrical, so mostly I ask leading questions and see what answers I get.
    – keshlam
    Sep 18, 2014 at 3:16
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    Would you really want a pipe running through the basement? It would require sacrificing space, clearances, and might provide objectionable noise in a bedroom or other quiet room.
    – wallyk
    Sep 18, 2014 at 5:17

2 Answers 2


In most US jurisdictions, from a legal perspective, the work in the basement would fall under the local building code and its permitting, licensing, and inspection requirements...e.g. a splinkler contractor could not run the pipes inside the house and a plumber would be required, building department fees would be applicable, etc.

The pipe running through the basement that conceptually would be part of the irrigation system, is both legally and from a life safety standpoint part of the domestic potable water supply [it may be possible to get the building department to treat it as a domestic non-potable system, but that's less likely than a flat "no" from the building department]. Even if you get it approved, you'd still want a vacuum break where the pipe exits the building and there's a risk of contamination.

Anyway from a practical standpoint, one thing you're facing is the standard practices of the irrigation installer tradebase. They own Ditchwitches and shovels. They don't usually dress for walking across homeowner carpets and aren't in the habit of pulling plumbing permits. This is pushing things outside their business model...and reducing their revenue. Maybe you see a portion of whatever savings the contractor realizes, maybe the contractor just passes on the job [it depends on how much work they have, and you want the person who is busy].

  • After talking to a number of contractors, this is exactly what I learned. There would be nothing wrong with this approach, but they cost saved was minor, as the time for a plumber to run a pipe through an interior space costs about the same as someone digging a trench through my side yard.
    – John
    Nov 14, 2014 at 17:43

I think this is a spectacular idea and a great way to save money on a project. Some advice for you though!

  • Branch off the main line After the cutoff valve.
  • Have the water company shut off your water at the street. Plumbers have told me that sometimes if you cut off the water using the emergency shutoff it can fail and not cut on again.
  • Put in a cutoff right after you branch off from the main line- in case something happens!
  • Put a reverse flow preventer on your line as well
  • Check to see what the frost line is in your area, and then make sure you bury your pipe well below that depth!
  • You may want to consider adding in a bleed point for your pipe - if you need to empty it for some reason!
  • In many jurisdictions, you don't have to depend on the water company to shut off the water at the street. I have it in writing from my water utility that they don't care. The covers have a 5 sided bolt to make it difficult, but a vice grip will get the cover off just fine. Once inside the shut-off is simple to operate. It's only illegal to touch that stuff if your intent is to steal service or tamper with the meter. Sep 25, 2017 at 15:13

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