The leak in my own yard: what five months of water data showed

I build software that watches irrigation water. This summer my own system leaked for five months before I found it.

The cause was ordinary. Water reaches my curb at 145 psi, and a pressure-reducing valve on the main line is supposed to bring it down to about 75. Sometime in late May that valve failed. With full street pressure behind them, the valves in my sprinkler boxes slowly gave out and started leaking around the clock, whether a zone was running or not. I shut the irrigation off on October 26 and had it repaired.

Looking back, what surprised me was how early the data knew.

About 24,000 gallons, about $244

In early June, the quietest hour of the night at my house used about a gallon of water. By mid-July that hour used 3 to 5 gallons, and by September it was 12 or 13, every hour, day and night. That's roughly 300 gallons a day going nowhere.

From June 1 to the shutoff, the leak added up to about 24,300 gallons. My water bill is tiered, and summer irrigation already had me in the top tier, so every leaked gallon was billed at the highest rate. With tax, it came to about $244. (My pool's autofill also runs off the irrigation line, so I've counted the water it took as part of the leak.)

Once the irrigation was off, the quiet hours dropped to zero.

The first warning came in May

Before anything leaked, my zones started using more water every time they ran.

Each sprinkler zone has a normal flow rate, measured in gallons per minute, and it barely moves from one run to the next because the heads, the pipe, and the pressure stay the same. A schedule change affects how long a zone runs, not how fast water moves through it.

On May 28, that rate jumped across the yard. Within about ten days, 7 of my 12 zones were moving 30 to 85% more water per minute. One went from 15 gallons a minute to 28; a drip zone went from 12 to almost 18.

Six days in, on June 3, a line broke several sprinklers while it was running. I had them repaired on June 5.

The flow rates never came back down. They stayed high all summer, because the repair fixed the sprinklers and not the regulator that broke them. Curb pressure kept coming through, and over the next few months it wore out the valves.

Why my own alerts stayed quiet

The flow monitor I built compares each zone with its own history and flags one that waters well above or below its normal. It's designed to catch a single broken head on a single zone.

It was also designed to accept a new normal. If a zone held a new rate for a handful of runs, I assumed something had changed on purpose (new heads, say), and the alerts stopped. That's the right call for one zone. Seven zones shifting in the same week point to one problem upstream of all of them, and the monitor treated it as seven separate new normals.

The valve leak was invisible to it for a different reason. The monitor only looks at water used while a zone runs, and a valve that leaks around the clock does most of its leaking when nothing is running.

What I built because of it

These went live on October 27. They're in beta, and subscribers can turn them on in Settings → Alerts.

• One alert when several zones jump at once. When most of the yard shifts the same way within two weeks, the likely cause is pressure rather than heads. You get one email that points to the pressure regulator first, and the affected zones keep their old normal until you say whether you fixed something or changed it on purpose. I replayed every account's run history against it, and it would have alerted me on May 30, four days before the first break.
• A check after repairs. When you mark a problem fixed, the next few runs are compared with the zone's old rate. If the flow doesn't come back, you hear about it, because whatever caused the problem probably wasn't the part that got replaced.
• Overnight water, with a price on it. The overnight alert now says how much is running, what it costs, and how that compares with a month ago: "About 300 gallons a day (about $90 a month), up from about 160 a day a month ago." It sends one more email if the flow doubles, along with a short checklist for tracking down the source, starting with the irrigation shutoff.

Next on my list is a second meter. Flume sees the whole house. Add a Moen Flo on the house side, and the difference between the two readings is everything outdoors, so an outdoor leak would show up as outdoor without anyone closing valves to find it.

If you have a Flume

Two things worth checking this week, whether or not you use Barranca Verde:

1. Look at your Flume's usage around 3 a.m. If there's flow every night, something is running that shouldn't be.
2. If you have a pressure gauge, screw it onto a hose bib. If it reads above about 80 psi, have a plumber look at your pressure regulator. Mine let nearly twice the intended pressure through for months before I knew.