A cistern level monitor for hauled water: order before you run dry

Order a load of water when the cistern falls to a line that leaves enough above the pump's intake to last until the truck comes, with a few days to spare. A level monitor turns that line into an alert, and its chart tells you how many inches a day your household really draws, so the line is set from your own use and not a guess.

Trivertix is one such monitor: a solar-powered ultrasonic sensor in the tank's lid, and a receiver in the house that shows the level with no subscription.

By Luke Patterson, co-founder of Trivertix. Last checked November 9, 2026.

The days left, at your own rate

Every household draws its own amount: more in summer, more with guests. A gauge on the tank shows today's level and keeps no record, so the rate is what a monitor's chart adds. Take the level a week ago at the same hour, take today's, and divide the fall by seven.

The days left are the inches above the pump's intake, divided by that rate. Do not count the water under it: as a tank seller's guide puts it, "your pump cannot draw the last of it."

The sums on this page are for an upright round tank 10 feet across, full at 9 feet of water, with the pump drawing from 6 inches off the floor. At 231 cubic inches to the gallon, each inch of it holds about 49.0 gallons.

The water the pump can reach, full: About 4,994 gallons
Drawn down 4 inches a day: About 196 gallons a day
From full to empty at the intake: About 26 days

For another width, the guide to reading a gauge has the gallons an inch. A tank on its side fills unevenly: go by its maker's chart. The four kinds of level indicator are compared on their own guide.

Source, read November 9, 2026: Tank Depot: How to size an underground cistern for a whole house.

Source, read October 7, 2026: NIST Handbook 44 (2026), Appendix C (PDF).

The low alert line is the order

Two lines on the tank decide when to call. Below the upper one a whole load fits. Below the lower one you are counting on the truck.

The hauler's wait: Up to 3 days, and 2 more to spare
The low alert line: 26 inches off the floor: the intake and 5 days at 4 inches
A load of 3,000 gallons: About 61 inches of this tank
Room for the whole load: Below about 47 inches
The time to call: About 5 days between the two lines, after about 21 days from full to the low line

One delivery company gives 1 to 3 days as its usual wait for a cistern fill. The tank seller's guide adds: "If your hauler is often booked up, add a few days." So set the low alert at the lower line, and call when the tank is between the two.

The same guide sizes a cistern to hold "a full truckload plus about a week of your household's use." This tank does: about 4,371 gallons, inside the 4,994 the pump can reach.

A load is sold whole. A directory of Texas haulers puts one at $150 to $500, with a minimum fee of $150 to $300 at most haulers. Order into a tank without room for it, and you pay for water left on the truck.

Sources, read November 9, 2026: McDonald Farms: Water delivery services, Tank Depot: How to size an underground cistern for a whole house.

Source, read October 15, 2026: HaulAgua: Bulk Water Delivery in Texas.

What a delivery looks like on the chart

A level read about every 15 minutes draws a saw: a slow fall, a sudden rise, a slow fall.

The step up

A delivery is one tall step between two readings: about 61 inches for a 3,000-gallon load on this tank. Times the gallons an inch, it is what went in, to set beside the bill.

A fall at night

A tank that drops while the house sleeps is losing water. The guide to a tank that drops overnight has a founder's running toilet, caught at eight inches.

Where Trivertix fits, and where it does not

It is made for closed storage tanks, cisterns and open stock tanks. The sensor is ultrasonic, mounted at the top of the tank and reading down to the water, and it reads tanks up to 16 feet deep. On a closed tank it takes a 4-inch opening in the tank lid. An adapter fits openings from 4.5 to 5.5 inches.

The receiver is a display for the tank level and four status lights. It plugs into the wall and joins your home Wi-Fi. It shows the level with no account and no plan. A monthly plan adds the app, on iPhone, Android and web, with the chart and one high and one low alert line: set the low one at your order line. What it costs is announced at launch.

It does not fit everywhere. The transmitter runs on a solar panel and rechargeable batteries, so it needs sun, and its radio needs a path to the house: a mile or more with a clear line of sight, less through hills and brush. A cistern inside a building or in deep shade is a poor place for it. It says nothing about what is in the water, and on a tank that a well fills, it reads the tank and not the well.

Finding a licensed hauler

In Texas, the Commission on Environmental Quality keeps the list of companies approved to haul drinking water, county by county, with each one's address. The household trade is thickest in the Hill Country west of Austin, in Hays, Blanco, Burnet and Travis counties. Few haulers there print a price: they quote by the address, the gallons and the length of the hose run.

Source, read November 9, 2026: Texas Commission on Environmental Quality: Licensed Water Haulers.

They are busiest when the wells are low. The Texas Water Development Board put 82 percent of the state in drought as of October 6, 2026, against 26 percent a year before. In March, KUT reported every well the Hays County groundwater district monitors below its historic level, and a deeper well costing upwards of $75,000. When the neighbors are ordering too, the days to spare count.

Sources, read October 15, 2026: Texas Water Development Board: Water Weekly for the week of October 12, 2026 (PDF), KUT: Hays County wells run drier as aquifers fall to their lowest levels in more than 20 years.

Questions about a cistern on hauled water

Is there a cistern level monitor with no monthly fee?

Yes, for reading the level at home. Trivertix shows it on a receiver in the house with no subscription: a display for the tank level and four status lights. It plugs into the wall and joins your home Wi-Fi. A monthly plan adds the app, with the chart of the level over time and the alerts on your phone. Other makers sell cistern gauges with a display and no fee as well, so ask each one whether the alerts on your phone come with it or with a plan. The Trivertix prices are announced at launch.

How do I find a licensed water hauler in Texas?

The Texas Commission on Environmental Quality publishes the list of companies approved to haul drinking water in the state, county by county, with each one's address. Few haulers print a price, so call with your address, the gallons you want and how far the hose has to run. A directory of Texas haulers puts a load at $150 to $500, with a minimum fee of $150 to $300 at most of them.

How much should a delivery raise the level in my tank?

The gallons delivered, divided by the gallons your tank holds for each inch. An upright round tank 10 feet across holds about 49.0 gallons an inch, so a 3,000-gallon load raises it about 61 inches. On a monitor's chart the delivery shows as one tall step up between two readings. A step well short of the load on the bill is worth a question to the hauler.

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