Water tank level indicators: the four kinds, compared
A water tank level indicator shows how full a tank is without anyone lifting the lid. There are four kinds: a float with a marker on the outside of the tank, a clear sight tube, a pressure gauge at the outlet, and an electronic sensor with a display.
By Luke Patterson, co-founder of Trivertix. Last checked October 7, 2026.
The four kinds, side by side
The first three are mechanical, and you read them at the tank. The fourth is the only kind that can show the level somewhere else.
| Float and marker | Sight tube | Pressure gauge | Electronic sensor | |
|---|---|---|---|---|
| How it shows the level | A float in the tank moves a marker along a scale on the outside wall. | Water stands in a clear tube beside the tank, at the height it stands inside. | A gauge at the outlet reads the weight of the water above it: about 0.43 psi a foot. | A sensor measures the level and sends it to a display, a row of lights or an app. |
| Where you read it | At the tank, from as far off as you can see the marker. | At the tank, up close. | At the gauge, on the tank or the pipe beside it. | In the house or on a phone, wherever the display is. |
| Power | None | None | None | Batteries, a solar panel or a wall plug |
| Tells you of a change | No | No | No | Many do, with an alarm or an alert at a level you set. |
| What to watch for | A cable or a pulley that sticks. On most, the marker sits low when the tank is full. | Algae in a tube that stands in the sun, and a split tube after a freeze. | A full tank 8 feet deep reads under 4 psi, so it takes a low-range gauge. | How far it reaches, and whether it needs Wi-Fi, a cell signal or a subscription. |
Source, read October 7, 2026: Waterworks Mathematics by Alvord and Blasberg, section 1.7.1.
Pick by where you need to read it
At the tank
If you pass the tank every day, a float and marker or a sight tube is enough. They are the simplest of the four and need no power.
From the house
To see the level without walking out to the tank, you need an electronic indicator with a display indoors: wired for a tank beside the house, wireless for one across the yard or the pasture.
From anywhere
To know the level while you are away, or to be told before the tank runs low, you need one that reports to a phone. That kind is usually sold as a tank level monitor.
Where Trivertix fits
Trivertix is the fourth kind. An ultrasonic sensor at the top of the tank reads down to the water, in tanks up to 16 feet deep. It reports by LoRa radio to a receiver in the house, and the receiver shows the level on its own display.
That much needs no app, no account and no monthly fee. A monthly plan adds the app, which shows gallons and the level over time on your phone, and sends an alert at a high or a low line you set.
It does not fit every tank. The receiver has to sit in a building with power, within radio range of the tank: a mile or more with a clear line of sight, and less through hills and brush. And if a glance on your way past is all you need, a float and marker gives you that with no electronics at all.
See how Trivertix worksQuestions about tank level indicators
What is the simplest water tank level indicator?
A float and marker. A float inside the tank is tied by a cable to a marker on the outside wall, and the marker moves along a scale as the water rises and falls. It has no electronics and needs no power.
Can I read a tank level indicator from inside the house?
Yes, with an electronic one. A sensor on the tank sends the level to a display indoors, by wire or by radio. A float and marker, a sight tube and a pressure gauge are all read at the tank.
Do water tank level indicators need power?
The mechanical kinds do not. A float and marker, a sight tube and a pressure gauge all work off the water itself. An electronic indicator runs on batteries, a solar panel or a wall plug.
What is the difference between a level indicator and a level monitor?
The two words overlap. An indicator shows the level now, to whoever looks at it. A monitor also keeps a record and can send an alert, so it tells you about a change you were not there to see.
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