Keeping track of an emergency water storage tank
To keep track of an emergency water tank without lifting the lid, put a level sensor in the lid that reports to a display indoors, and set a low alert line just under the full mark. Nobody draws from a tank kept in reserve, so its level should hold flat, and any fall the sensor sees is water leaving it: a leak, a weeping valve or a tap someone left open.
Trivertix does this with a solar-powered ultrasonic sensor in the lid and a radio link to a receiver in the house, which shows the level with no subscription.
By Luke Patterson, co-founder of Trivertix. Last checked October 13, 2026.
Why a stored tank is the easy one to watch
A tank that feeds a house rises and falls all day, and a leak hides among the use. A tank kept for an emergency should do nothing at all, so a reading taken through the day and kept makes any change stand out. The shape of the line tells you what kind of change it is.
A flat line
The tank is full and holding. This is the picture you want to see every time you look, and the one the rest is held against.
A slow, steady fall
Water is going somewhere: a fitting that weeps, a drain valve that does not quite seat, or a crack. It does not stop at night, which is how you tell it from use.
A fall that stops partway down
A leak in the side of the tank drains it down to the hole and no farther. The level where the line goes flat again is about the height of the leak, which tells you where to look.
A sudden step down
Someone drew water: a hose left on, or a hand on the wrong valve. On a tank meant to be left alone, any step is worth a question.
One shape is not a leak. An ultrasonic sensor times an echo, and sound travels slower in cold air, so the reading can shift a little between a cold morning and a hot afternoon. That moves back and forth with the weather. A leak only goes one way. The guide to tank level sensors works out how large the shift is.
What a slow leak looks like in inches
A small leak takes a while to show, and the time it takes depends on the tank's width and on how small a change the sensor can see. The sums below are for an upright round tank 8 feet across, which holds about 31.3 gallons for each inch of depth at 231 cubic inches to the gallon.
- One step of the sensor
- A quarter of an inch, or about 7.8 gallons on this tank
- A leak of 1 gallon a day
- One step in about 8 days
- A leak of 10 gallons a day
- One step in about 19 hours
So a weep you would never see on the ground shows within about 8 days, and keeps showing a step at a time after that. Measured against the ration the emergency agencies use, 1 gallon for each person each day, one step on this tank is about 8 days of water for one person, gone.
A tank checked by eye once a season can lose a great many steps between looks. A reading taken about every 15 minutes finds the leak in days.
Source, read October 7, 2026: NIST Handbook 44 (2026), Appendix C (PDF).
Source, read October 13, 2026: Ready.gov (FEMA): Water.
What the stored water is for
In February 2021 a freeze broke water service across Texas. A spokesperson for the Texas Commission on Environmental Quality said on February 17 that service had been disrupted for more than 12 million Texans, and that nearly 680 water systems had issued boil water notices. A tank of water at the house is one way to be ready for the next one, as long as the water is still in it when the day comes.
Source, read October 13, 2026: NBC News: Texas contending with water nightmare on top of power crisis.
- How much a day
- Ready.gov, from FEMA, says to store at least 1 gallon of water per person per day, for drinking and sanitation. The CDC gives the same figure for at least 3 days, and asks for a 2-week supply if possible.
- In the heat
- Ready.gov notes that in very hot weather a person's water needs can double, so a tank sized in spring can fall short in August.
- Keeping it fresh
- Both say to replace water you store yourself every 6 months. The CDC asks for a cool place, 50°F to 70°F.
Replacing the water is a natural time to look over the tank: drain it, see the level fall and rise on the chart as it empties and fills, and check that the line goes flat again once it is full.
Sources, read October 13, 2026: Ready.gov (FEMA): Water, CDC: How to Create an Emergency Water Supply.
How Trivertix reads the tank
- The opening
- A 4-inch opening in the tank lid. An adapter fits openings from 4.5 to 5.5 inches.
- The sensor
- Ultrasonic, mounted at the top of the tank and reading down to the water. It reads tanks up to 16 feet deep.
- What it reads
- Water level in gallons and percent full, plus water and air temperature. The temperature tells you, on a winter night, how close the water is to freezing.
- The power
- Solar panel and rechargeable batteries, so it needs sun on the tank and no wire from the house.
- The readings
- About every 15 minutes.
The reading goes by LoRa radio at 915 MHz to a receiver in the house, with no SIM card and no cellular plan, so the link does not lean on a cell tower. A mile or more with a clear line of sight; three-quarters of a mile through hills and mesquite on our pilot ranch in Karnes County, Texas. The receiver shows the level with no account. A monthly plan adds the app, on iPhone, Android and web, with the chart of the level over time and one high and one low alert line.
Where it fits, and where it does not
It fits
- Closed storage tanks, cisterns and open stock tanks, including a tank kept full for an emergency.
- A tank within about a mile of the house, with sun on it.
- A household that wants to know the reserve is still there without opening the lid.
It does not cover
- Jugs, barrels and drums with only a small cap. The transmitter sits in a 4-inch opening in a lid.
- A power cut indoors. The receiver is a display for the tank level and four status lights. It plugs into the wall and joins your home Wi-Fi. The sensor on the tank runs on its own panel and batteries, but plan to check the tank by eye in a long outage.
- Whether the water is safe to drink. It reads the level and the temperature, not the quality of the water.
Questions about an emergency water tank
How can I tell if a stored water tank is leaking without checking it every day?
Watch its level over time. Nobody draws from a tank kept for an emergency, so its level should hold flat, and a line that keeps falling day after day is water leaving it. A sensor that reports a change of a quarter of an inch sees about 7.8 gallons go from a tank 8 feet across, and a low alert line an inch or two under the full mark turns a leak that keeps going into a message on your phone.
How often should water stored for an emergency be replaced?
Every 6 months for water you store yourself, by the advice of both FEMA's Ready.gov and the CDC. Ready.gov puts it as water that has not been commercially bottled. The CDC also asks for a cool place to keep it, 50°F to 70°F.
Where should I set the low alert on an emergency water tank?
An inch or two under the level you filled it to. A tank kept in reserve should not fall at all, so there is no day's use to leave room for. On a tank 8 feet across, an inch is about 31 gallons. Set it much closer than an inch and a cold morning can trip it, since an ultrasonic sensor reads the water a little farther away in cold air.
Read next
A monitor for a storage tank fed by a well
The same monitor on a tank the household draws from every day.
Tank level sensors and how accurate each is
Ultrasonic, pressure and float, and why cold air fools an ultrasonic one.
How to read a water level gauge
And how to turn the reading into gallons for a tank of any width.
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