I cut my water bill from $74 to $41 in 30 days. Here's the leak audit.

My water bill in March said $74. I live alone. I do not have a lawn. I do not own a hot tub. Something was wrong, and the something turned out to be three things, and all three were fixable in a weekend with about $12 in parts.

April’s bill: $41. Here’s exactly what I did.

Step 1: The midnight meter test

This is the one diagnostic that tells you whether you have a leak at all, and it costs nothing. Find your water meter. (Outside the house, usually near the curb, under a metal lid that says WATER. If you rent, ask your landlord — they’ll usually walk you to it because they don’t want to pay for leaks either.)

The night before bed:

1. Make sure no faucets are running, no toilets flushing, no dishwasher or washing machine going, no ice maker filling.
2. Read the meter. Write down the number to the last digit.
3. Don’t use any water overnight.
4. Read the meter again first thing in the morning before you flush, run a tap, anything.

If the second number is bigger than the first by even a fraction, you have a leak. Mine moved by 4 gallons overnight, with zero usage. That’s the equivalent of about 120 gallons a month leaking out somewhere. That alone is roughly $8-15 on most US municipal water rates.

Step 2: Find the toilet leak (it’s almost always the toilet)

EPA estimates that household leaks waste nearly 1 trillion gallons of water nationwide every year, and the largest source by volume is toilet flapper valves. They wear out, they don’t seal, they let tank water trickle into the bowl 24/7, and you never hear it.

The food-colouring test takes 15 minutes:

1. Drop 5-10 drops of food colouring into the tank (the back of the toilet, not the bowl).
2. Don’t flush.
3. Come back in 15 minutes.
4. If the colour shows up in the bowl, your flapper is leaking.

Both of my toilets failed this test. One was bad enough that the bowl was lime green in 4 minutes.

Replacement flapper kits at Home Depot or Lowe’s: $4-8 each. Installation: 8 minutes per toilet, no plumber needed, no tools beyond your hands. There are 90-second YouTube videos for every model. This single fix is, by a wide margin, the highest-leverage water-bill move in the entire US.

For me: two $5 flappers, 16 minutes total, ~$18/month off the bill.

Step 3: The faucet aerator + showerhead swap

Old aerators (the little screen at the tip of every faucet) flow at 2.2 gallons per minute. New WaterSense-labelled aerators flow at 1.0-1.5 gpm, with no perceptible difference because the device aerates the stream. They’re $1.50-3 each at any hardware store.

I swapped three: kitchen, bathroom sink, second bathroom sink. Total cost: $6.

Showerhead: same idea, bigger swing. Old showerheads flow at 2.5 gpm or worse. WaterSense-labelled ones flow at 1.5-2.0 and most people can’t tell the difference. A decent low-flow head is $15-25. Mine was 13 minutes old at this point and had clearly been the previous tenant’s.

This batch of swaps is harder to attribute precisely to the bill, but the EPA’s WaterSense calculator gives a typical household savings of about $130/year on water + heating from these two changes alone, or roughly $11/month.

Step 4: The phone call to the city

Most US municipal water utilities have a “high bill investigation” or “leak adjustment” program that almost nobody uses. If your bill spiked and you can prove a fix (receipts for plumber or parts, before/after meter readings), they will often credit a portion of the spike on your next bill. Not all cities. Most.

I called my city’s water department, said “I had a leak, I fixed it, I have receipts, can you investigate?” They asked for the meter reading, the dates, and a photo of my receipts. Two weeks later they credited $14 to my next bill. I had no idea this program existed before I made the call.

Worth 10 minutes of your time. Worst case they say no.

The full 30-day math

Fix	Cost	Monthly saving
Two flapper valves	$10	~$18
Three faucet aerators	$6	~$5
Low-flow showerhead	$22	~$8
City leak credit (one-time)	$0	$14 (one bill)
Total parts	$38	~$31/month ongoing

Bill went from $74 to $41. Parts paid for themselves in 5 weeks. Still saving $30+ a month a year later.

What didn’t work

Two things I tried that weren’t worth the bother:

• A “shower timer.” Lasted three days. I’d ignore it. The showerhead swap was a much better intervention because it doesn’t depend on me changing my behaviour.
• Fixing a slow drip in the bathtub spout. Cost $8 in parts and required a wrench I had to borrow. Saved maybe $0.30/month. I learned a lot about cartridge faucets but the math wasn’t there.

What to do this weekend

1. Saturday morning, midnight meter test. Free. Tells you if you have a leak.
2. Saturday afternoon, food colour test on every toilet. Free except the food colouring.
3. Hardware store run. $15-30, depending on what’s broken.
4. Sunday: 30 minutes of installs. No plumber.
5. Monday: call the city and ask about their leak adjustment program.

The whole audit is under $40 and probably 90 minutes of work. For most US households it pays back inside two months and keeps paying after.

If your water bill keeps creeping up after this and you can’t find a leak, the next conversation is about your municipal rate structure (most US cities use tiered pricing) or about appliance replacement, but start here. The $4 flapper is the highest-leverage utility fix in your house.

For the bigger picture, run your full bills through the 50/30/20 calculator — water is small but the same audit logic applies to every line in the needs bucket.