I recently received a notification from my water department that they suspect I have a leak somewhere in my house. Apparently, the meter outside has a mechanism that goes off if water has been running for 24-continuous hours.

As a test, I tried turning off all water in the house and checking the meter. Then, approximately 20-30 minutes later, I checked the meter again and compared numbers. Sure enough, I had gone through 1/3 of a gallon.

Now comes the fun part -- finding the leak. I've checked:

  • Water supply valves and spouts.
  • Toilets (placing dye tablets in toilet tanks)
  • Major appliances (refrigerator, dish washer, clothes washer, etc)

The only thing I found was a extremely small leak in the toilet water supply valve. I'm in the process of replacing the valve but I'm skeptical this is it.

When I periodically check my water meter, it looks like I'm leaking approximately 1 gallon an hour.

One thing seems odd: when I stand close to the water main line as it enters the house, I hear a faint hissing sound.

So my question is this: Is a faint "hissing" sound from a water inlet pipe a good indication that water is in use? Can I trace that sound to the source? Or is this a red herring and could be caused by something else?

  • It's quite likely that you're hearing water flow through the valve, though not sure that's going to help you find the leak. Good luck, though. Looks like this one is a challenge.
    – DA01
    Jan 26, 2016 at 3:57
  • Do your toilets make any noise at all, such as a faint hissing noise, dripping, etc? Have you checked your exterior hose bibs for leaks?
    – user4302
    Jan 26, 2016 at 5:20
  • 8
    Did you try shutting off the main valve? There is a remote possibility your leak is after the meter but outside the house. Try the same test you made but with the main valve shut off to see if the leak is after the main valve.
    – ArchonOSX
    Jan 26, 2016 at 8:34

1 Answer 1


The most common leaks that don't show themselves (damage, or water on the ground) are either inside toilets (the toilet leaks water from the tank to the bowl) or in the water line outside the house.

Right where the water line comes into the house there should be a valve. The first place I would start is to turn off the main valve in the house then check the meter. Leave it for a few hours and check it again. If the meter has turned then the leak is underground and it will be a pain to fix. I've heard that if you do confirm that that's the problem, some professionals have an expensive tool to find such leaks. If you don't have a valve right where the water enters the house I would seriously consider starting by adding one in (or have a plumber do it).

If that's not the problem I would put a bunch of food coloring in the tanks of all the toilets (not the bowls) and check in a while to see if the color has leaked down into the toilet bowls. If any of the toilet bowls do have color in them, that right there is a leak that doesn't cause any damage, but does waste water.

Some water heaters can absorb some water into the insulation, making it less obvious that it's leaking but once the insulation is saturated, that wouldn't really make a difference.

Other than that, watch carefully for any signs of water or water damage near the base of all of your walls, on all of your floors (especially near the walls), and in all of your ceilings. Regularly check all around your water heater (especially around the unions, T&P valve, valves, and the base).

If you don't find anything I would seriously consider getting a plumber (especially if you know one) because water damage can be very costly. Not being a plumber myself, I don't really know how much they can do to track a leak but I'm sure they would know more than a DIYer like me.

I hope this helps.

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