We have a hill in our backyard. When we started to take out some room for a retaining wall, we found that the hill is leaking water about a foot off of the ground level. We turned off the sprinkler system and water is still pouring out from inside the hill. We do have about three high-pressure valves to push the water up the hill. My question is, how do we find the source of the water?

Hill, leaking (video)

In addition to the video above, please fine a pictures of the hill below.

Hillside showing pipe layout

Our current plan is to build up the retaining wall and we do plan to put a French drain behind it. We are interested in the source of the water. We’ve had the sprinkler controller off for almost a week. I can see that the hill still appears to be saturated with water.

There are some high pressure pipes on the right hand side of the hill connected to pipes that supply water. Those pipes are above ground and so far we have not seen any leakage from the pipes above ground.

There are more sprinklers up on the hill, so I’m guessing that at some point pipes must be in the ground. Do I need to start digging up around the sprinklers or is there a better method to locate potential leaks?

Actually, I just recalled that we did remove two sprinklers from below and in front of the ground area where the leak is occurring. We capped the pipes after verifying that they were not leaking. The issue is that the water is coming from above where the removed sprinklers are located. This fact makes me think that perhaps a pipe in the hill associated with one or more of the other sprinklers (not the ones we removed) is broken.


I've been thinking about it for quite a while now and I think that the most likely thing that could be going on with the leaks is this- we have high pressure supply lines that feed into regular sprinkler lines underground. The high pressure is causing leaks similar to what we saw when we dug out the two sprinklers. Just imagine that happening at all the sprinkler heads because the high pressure needed to push the water up the hill it's too high for the regular sprinkler pipes to contain. I just don’t know how to reduce the pressure on the supply lines. Is there also way to verify the pressure?

  • Pictures will help. I imagine it is a good size hill so either leaking pipes or a natural stream. The pipes could have been leaking for a long time and saturated the hill, so will need a long time to dry out. If a natural stream, then drainage is in your future.
    – crip659
    Jun 24, 2023 at 23:42
  • 1
    Grab a copy of "Mr Blandings Builds his Dream House" from the library and read it.
    – Ecnerwal
    Jun 25, 2023 at 0:19
  • 1
    It's not clear what exactly you're talking about. Are you building a retaining wall to claim some additional flatter ground closer to the house? Why do you have sprinklers on the hill? Are you sure it's not just groundwater? You were planning to put an underdrain behind the wall anyway, weren't you?
    – Huesmann
    Jun 25, 2023 at 13:13
  • With the sprinkler system off, can you check how much water you consume in a week and can you account for all of it? That should tell you if you have a leak or not. Jun 25, 2023 at 15:58

1 Answer 1


Likely you've hit a spring, if it's still weeping a week after shutting off the irrigation.

(Thus my book recommendation. After spending lots of money to drill a rather deep well to get water, Mr. Blandings then hit a spring when blasting the basement hole quite nearby, but in a different spot.)

So, install a water feature, (and drainage) or be boring and just install drainage.

Or put non-toxic tracing dye in the sprinkler system and turn it back on, then look for color in the weep. Which would be an indication that it was from a leaky sprinkler system.

Alternatively, you could test the water for various things and see how it is the same or different as your domestic supply source - for instance, if your supply is chlorinated, or hard, or of a particular pH, and the water from the hill tests basically the same, you would suspect leakage, while it being significantly different would point to a different (natural) source. Though chlorination can be stripped in a relatively short amount of travel through soil...(but if any is seen, that's not likely to be natural.)

  • I’m a little unclear about installing a water feature. Could you elaborate please?
    – Tommie C.
    Jun 25, 2023 at 20:49
  • Run it into a small (or large, if you like) pool, waterfall or fountain. Provide an overflow from that to drainage. Quite common for springs in old gardens, predating electric pumps.
    – Ecnerwal
    Jun 25, 2023 at 20:58
  • I provided some updated findings. Can you take a look and let me know what you think?
    – Tommie C.
    Jun 26, 2023 at 5:32

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