Well systems: pressure tanks, switches, and what is really wrong

What we do, and what belongs to a well contractor

Being clear about this saves everyone time. Private wells involve two different trades and the boundary sits at the well head.

House-side work, ours. The pressure tank, the pressure switch and controls, the pipework and valves from the well head into the house, jet pumps and above-ground pumps, storage tanks and booster pumps, filtration and treatment, and the diagnosis of pressure and flow problems. This is where the substantial majority of complaints actually originate.

Well-side work, a well contractor. Drilling and deepening, the well casing, the submersible pump down the hole, pulling and setting a pump, drop pipe and wiring in the casing, well permits and registration, and anything to do with water rights or static water level. There are good reasons that is a separate license, and pulling a pump from a deep well needs a rig, not a van.

We also do not do water quality testing for certification purposes, or well permitting. Sampling for coliform and nitrate goes to a certified laboratory, and permits go to the state. We will tell you when a test is what you actually need, and we will fit treatment appropriate to results you already have.

What that means in practice: call us for pressure, cycling, tank, switch, treatment and plumbing problems. If the diagnosis points down the hole, we will say so rather than sell you a tank you did not need.

How a private system actually works

Understanding the sequence makes every fault on this page easier to interpret.

A submersible pump sits down the well and pushes water up to the surface. It does not run continuously. Instead it fills a pressure tank, which holds water under pressure against a cushion of compressed air behind a bladder or diaphragm. A pressure switch watches the pressure: when it falls to the cut-in point the pump starts, and when it reaches the cut-out point the pump stops. Between those two points, the tank supplies the house without the pump running at all.

That is the entire design intent: the tank exists so the pump runs in reasonable bursts rather than starting every time someone washes their hands. A pump motor is worn out by starts, not by running, which is why a failed tank kills pumps.

Downstream of the tank comes whatever treatment the water needs, sediment filtration first, then softening or specific treatment, and then the house. Every symptom people report is a disturbance somewhere in that chain, and the position of the fault is usually deducible from the symptom.

No water at all

Work through this in order before assuming a pump failure, because several of the causes are trivial.

Power. Check the breaker for the pump and any disconnect switch near the pressure tank or the well head. Pumps trip breakers, and a tripped breaker is a symptom rather than a cause, if it trips again immediately, stop and get it looked at rather than resetting repeatedly.

The pressure switch. Look at the gauge. Zero pressure with a pump that is not running suggests the switch is not calling for the pump, or has failed. Pressure that reads normal while no water comes out of a tap points downstream at a closed valve, a blocked filter or a frozen line rather than at the pump.

Filters. A completely blinded sediment filter can effectively stop flow to the house. It is worth checking before anything else, and on well systems with high sediment it happens more often than people expect.

Loss of prime on a jet or above-ground pump, which needs repriming and then an explanation for why prime was lost.

If power is present, the switch is calling, and there is no pressure and no water, then the problem is likely the pump or the well, and that is where a well contractor comes in. One genuinely local possibility deserves mention: across parts of rural Arizona declining groundwater levels mean some wells simply do not deliver as they used to, and a pump set too high for the current water level will pump air. That is not a plumbing fault and no amount of house-side work fixes it.

Short cycling: the most common fault on private systems

If the pump clicks on and off rapidly, every few seconds while a tap runs, or repeatedly when nobody is using water, this is the fault to look for first, and it matters more than it sounds.

Rapid cycling destroys pumps. Each start puts a heavy load on the motor, and a system that cycles ten times where it should cycle once ages the pump ten times as fast. People replace a pump, do not fix the cause, and replace another pump.

The overwhelmingly likely cause is a waterlogged pressure tank. The tank has lost its air charge, either because the bladder has ruptured or because the pre-charge has leaked away, and a tank full of water has almost no capacity to store pressure. There is nothing between cut-in and cut-out, so the switch chatters.

Diagnosing it is quick. With the pump isolated and the tank drained, an empty tank should feel light and sound hollow; a waterlogged tank is heavy and dull. On a tank with an air valve at the top, checking the pre-charge against the switch cut-in setting with the tank drained tells you directly. Water coming out of the air valve is a ruptured bladder and a definite replacement.

Other causes: a failed pressure switch, a clogged switch tube, a closed or restricted valve between tank and switch, or a tank grossly undersized for the household’s demand.

Pressure tanks and how they fail

The pressure tank is the component most likely to need attention on a mature system, and the one most often misdiagnosed as a pump.

Modern tanks use a bladder or diaphragm separating an air charge from the water. They fail in a few predictable ways: the bladder ruptures and the tank waterlogs; the air pre-charge bleeds away over years; the tank corrodes internally, sometimes visible as rusty water after a period of non-use; or the fittings and the tank tee corrode and weep. Older galvanized tanks without a bladder rely on an air cushion in direct contact with water and lose it steadily, which is why they need periodic recharging and why replacement is usually the better answer.

Two points about specification, because they decide how long the next one lasts. Size: a bigger tank means longer pump run times and fewer starts, and on a system that has been cycling hard, going up a size is often the fix rather than the luxury. Pre-charge: a new tank has to be set to match the switch cut-in pressure, and a tank installed without that step will not deliver its rated capacity. It is a five-minute step that is skipped often enough to be worth asking about.

Any tank replacement is also the moment to look at the tank tee, the gauge, the switch, the isolation valve and the drain, because they are all right there and they are all cheap compared with the labor of reaching them again.

Pressure switches, gauges and controls

The switch is a small, inexpensive electromechanical part that does a great deal of work, and it wears.

Symptoms of a failing switch: the pump will not start, or will not stop; pressure that overshoots or never reaches cut-out; visible arcing or pitted contacts; and cycling that persists after the tank has been proved good. The small tube or port that feeds pressure to the switch can also clog with sediment or mineral deposits, which makes the switch read the system incorrectly, a common and easily missed fault on well water.

A dead gauge is worth replacing whenever anyone is working on the system, because every diagnosis on this page starts with reading it, and a stuck gauge sends people down the wrong path.

Some systems use a constant-pressure or variable-speed controller instead of a conventional switch, varying pump speed to hold steady pressure. They are genuinely nicer to live with, particularly on properties with long runs or big demand swings, and they reduce cycling substantially. They are also more complex, and diagnosis is a different exercise, if you have one, say so when you call.

Low pressure and low flow

These are different complaints and separating them speeds up the diagnosis. Low pressure is a weak push at every fixture. Low flow is adequate pressure that collapses when more than one thing runs.

On the house side, the usual causes are a switch set low, a waterlogged tank giving no reserve, blinded sediment filters, a scaled or fouled treatment unit, a partially closed valve, or narrowed older galvanized pipework. All of those are addressable, and filters are the first thing to check because they are the cheapest and the most frequently guilty.

On the well side, a pump that is worn, undersized, or set at a depth that no longer suits the water level produces exactly the same symptoms, as does a well whose yield has genuinely declined. Distinguishing the two is largely a matter of watching what the pressure does during a sustained draw: a house-side restriction shows normal pressure that drops across the restriction, while a supply limitation shows pressure the pump cannot rebuild.

Where the well yield is real but low, the answer is often not a bigger pump but a storage tank with a booster pump, let the well recover at its own rate into storage, and pressurize the house from the tank. That is a house-side installation, and it is a common solution on rural Arizona properties.

Well water quality and treatment

Private wells are not treated by anybody. Whatever is in the aquifer at your address arrives at your taps, and Arizona groundwater varies enormously across the state.

What owners here commonly deal with: hardness, frequently higher than municipal supply, scaling heaters and fixtures; sediment and sand, particularly after pump work or in a well drawing from unconsolidated material; iron and manganese, showing as staining and metallic taste; hydrogen sulphide, the rotten-egg smell; nitrate, which matters in agricultural areas and is a health rather than nuisance concern; arsenic and fluoride, which occur naturally in parts of Arizona groundwater; and bacterial contamination after flooding, well work, or a compromised cap.

The order of operations is what people get wrong. Test first, then treat. Send a sample to a certified laboratory, get real numbers, and specify treatment against those numbers. Fitting a softener when the problem is iron, or an under-sink filter when the problem is nitrate, wastes money and leaves the issue in place. Testing annually for coliform and nitrate, and less often for the fuller panel, is the standard advice for a private well, and it is worth following.

Once you have results, the treatment train is normally sequential: sediment filtration first to protect everything after it, then iron or sulphide treatment if needed, then softening, then point-of-use reverse osmosis for drinking water where arsenic or nitrate are in play. See also whole-house water filtration. We fit and service that equipment; the laboratory does the testing.

Storage tanks, hauled water and booster pumps

A significant number of rural Arizona properties do not run directly off a well at all. Some haul water. Some have a low-yield well feeding storage. Some are on a shared or community system with poor delivery pressure. All of them end up with the same architecture: a storage tank and a booster pump.

The house-side work is much the same in each case, a tank, a booster pump, a pressure tank, a switch or constant-pressure controller, and treatment. The details that matter are float and level controls that actually protect the pump from running dry, an accessible and serviceable arrangement rather than a tangle in a shed, and freeze protection where the property is at elevation.

It is worth saying that these systems are frequently assembled incrementally over years and end up inefficient and hard to service. Rationalising one, sensible valve arrangement, isolation for each component, unions where they are needed, a gauge you can read, makes every future visit shorter and cheaper, and it is a good thing to do at the same time as replacing a tank or pump.

Seasonal and off-grid properties

Well systems and long absences interact badly, and much of rural and high-country Arizona is seasonal.

A property left for months brings the usual vacant-home risks plus a few of its own: stagnant water in the pressure tank and treatment equipment, a pump that sits idle and is then asked to start against a waterlogged tank, and freeze exposure at elevation where the tank and pipework are frequently in an unheated shed or outbuilding rather than inside the house.

The sensible routine is the same as any closing-up, with additions: isolate and depressurise, bypass the softener, deal with the water heater, protect anything exposed to freezing, and on return open up slowly and flush the system thoroughly before drinking the water. Water that has sat for months in a tank and a treatment train should be flushed and, on a well, is a reasonable moment to test. See vacant home water shutoff and prep.

One final practical note for anyone who has just bought a rural property: find and photograph the pressure tank, the switch, the isolation valves, the well head and the breaker, and confirm the valves turn. On a private system there is no utility to call, and knowing your own installation is the difference between an inconvenience and a week without water.