Equipment
The submersible pump gets water out of the ground. The booster pump is the one that decides whether the top-floor shower is any good. They are sized by different numbers, fail for different reasons and should never be asked to do each other's job. This guide covers the house-side pump: the two figures that size it, fixed speed against constant pressure, twin sets, suction, protection and the mistakes we are called out to undo.
November 2, 2026 · 10 min read
Most pressure complaints we see in villas are not the well's fault. The bore produces, the tank is full, and the shower on the top floor is still feeble, because the pump between the tank and the taps was bought by horsepower, or by what the shop had, or because it was the same model the builder used on a bungalow. The booster is the most used machine on the property: it starts every time anyone opens a tap. Sizing it properly is a short calculation, and the difference between the right pump and the nearly right one is the difference between a system nobody thinks about and one that is replaced every few years.
The well pump lifts water from the bore to the storage tank at whatever rate the bore can sustain. Its duty is set by the well: dynamic water level, yield and the height to the tank, which is why it is chosen from a pumping test. The booster pump takes water from the tank and delivers it to the house at whatever rate the house demands in its busiest ten minutes. Its duty is set by the building: how many outlets can run at once, how high the top one is, and what pressure a shower needs. The storage tank between them is what lets each pump do one job. Villas that try to feed the house straight from the submersible get the worst of both: a pump cycling on every tap, pressure that depends on the water level in the bore, and a well drawn down by a dishwasher. The reasons the tank should be the break between source and house are in how a villa water system works.
Flow is the volume the house can draw at once, not its daily use. Count what realistically runs together in high season: two or three showers at roughly 10 litres a minute each, a kitchen tap, a washing machine filling, perhaps a garden tap. A five-bathroom villa with six guests commonly lands between 30 and 40 litres a minute at peak, around 0.5 to 0.7 litres a second. Pool filling and irrigation are kept off this figure by giving them their own line; a pump sized to run sprinklers and showers together is oversized for everything else it does, which is the subject of our guide to garden irrigation from a well.
Head is the pressure the pump must produce, counted in metres. It is three things added up: the height from the water level in the tank to the highest outlet, the pressure you want at that outlet, and the losses on the way. A comfortable shower needs around 2 bar at the head, which is 20 metres; 3 bar is generous. Losses come from pipe length and diameter, bends, and above all from treatment: a sediment filter, an iron filter and a softener in series can take a bar between them when they are due for service, which is why the booster is sized with the treatment train's pressure loss included. A typical hillside villa works out at something like 8 metres of lift, 25 metres for the outlet and 7 to 10 metres of losses: a duty point of 35 litres a minute at 40 to 43 metres. The pump is then chosen so that its curve passes through that point in its efficient middle, not at the far right end where it is straining or the far left where it is doing almost nothing.
The traditional arrangement is a single-speed pump with a pressure switch and a pressure vessel. The switch starts the pump when pressure falls to a cut-in value, say 2 bar, and stops it at a cut-out, say 3.5 bar; the vessel's drawdown volume lets small draws be met without a start. It is simple, robust, cheap to buy and cheap to repair, and it tolerates the island's electrical supply reasonably well. Its drawbacks are the ones you feel in the shower: pressure wanders between the two switch settings as the pump cycles, and every start is a surge through the pipes. Get the vessel wrong and the pump short-cycles itself to death; our guides to pressure tanks and to pumps that keep turning on and off cover both.
A variable-speed set uses an inverter to change the pump's speed continuously so that the discharge pressure stays at one set value whether one tap or five are open. The pressure vessel shrinks to a few litres, starts are ramped rather than slammed, and at partial load the pump draws noticeably less power than a fixed-speed unit doing the same work. For a large villa with several bathrooms and guests who notice, it is the better experience. What it costs, apart from the price, is sensitivity: the electronics dislike the voltage swings and surges that island supply delivers, so a constant-pressure set belongs behind the same surge and voltage protection a well pump should have, and it should be a brand with a dealer on the island who can diagnose a controller, not only swap it.
Two ways to pressurise a house
Both draw from the storage tank and feed the same risers. They differ in how pressure is held between the outlets opening and closing.
The pump sits below the tank's water level, so the suction pipe is always full. Short, large-bore, with an isolating valve and a strainer.
Runs at full speed or not at all. Sized so its curve passes the duty point (peak flow at total head) in its efficient range.
The switch starts the pump at cut-in and stops it at cut-out; the vessel's drawdown absorbs small draws. Pressure drifts between the two settings.
Holds the pressure in the house side when the pump stops, so the pump does not restart because of backflow.
An inverter varies the speed to hold one set pressure as taps open and close. Soft start, lower part-load energy, quieter.
A few litres: enough to stop the controller hunting on a dripping tap, no longer a store of pressure.
Height to the top outlet plus the pressure wanted there plus pipe and filter losses is the head the pump must make.
A float switch in the tank, or the controller's own sensing, stops either pump when the tank is empty. Both kinds are destroyed by running dry.
Above a certain size, one pump is a single point of failure for every shower on the property. A twin set puts two pumps on a common suction and discharge manifold under one controller, either as duty and standby, where the second starts only if the first fails or is being serviced, or as duty and assist, where the second joins in at peak demand. The controller alternates which pump leads so that both wear evenly. For a villa that rents at full occupancy, or a resort with a dozen rooms, the second pump is cheaper than the first lost booking. The planning side of that is in water for a villa development.
A booster pump is happiest with flooded suction: installed below the water level of the tank, so water flows into it by gravity and it never has to pull. That means an above-ground tank with the pump beside its base, a short and generously sized suction pipe with no high points to trap air, an isolating valve and a strainer. Ask a surface pump to lift from an underground tank instead and it needs a foot valve, priming, and a suction line that stays airtight for years; the lift it can manage is limited and shrinks with every metre of pipe and every bit of air. Where the tank has to be underground, a submersible booster sitting inside the tank, or a properly self-priming set, is the honest answer, not a surface pump at the end of a long thin pipe.
Dry-run protection is the one that matters most: a booster that keeps running on an empty tank destroys its seal and bearings in minutes. A float switch in the tank that cuts the pump, or a controller that senses the loss of flow and pressure, is not optional. Beyond that: overload protection sized to the motor, surge protection on an inverter set, a non-return valve on the discharge, isolation valves on both sides so the pump can be changed without draining the house, and a location out of the sun and rain with air around the motor. A pump that cooks in a tin box in April will not last.
A new booster is set, not just switched on. On a fixed-speed set, the pressure switch cut-in and cut-out are adjusted to the system and the vessel's air charge is set just below cut-in. On a variable-speed set, the setpoint is chosen for the top floor rather than the plant room. Then the test that matters: two showers running on the highest floor while someone reads the pressure at the furthest outlet, and the motor current checked against the nameplate. The numbers, together with the settings, go on a label on the pump and in the villa's records, next to the well's. Our villa water system overview explains how that record fits with the rest of the plant.
If the top floor is weak, the pump cycles, or you are choosing a booster for a new build, our pump installation team works out the duty point from your outlets and your treatment, and specifies and commissions a set that holds it.
Equipment
Weak showers are a symptom with half a dozen possible causes between the storage tank and the tap. The fastest way to the right fix is to notice when the pressure is low, where, and whether the tank is full at the time. This guide turns those three observations into a diagnosis.
August 19, 2026 · 9 min read
Equipment
The small steel tank beside the booster pump is not a water store. It is a cushion of compressed air that lets the pump rest between starts. When the cushion goes, the pump starts on every draw and the pressure jumps. This guide explains how the vessel works, what it needs, and how to recognise one that has failed.
September 13, 2026 · 9 min read
Equipment
A pump that keeps starting and stopping is usually obeying its controls exactly. The question is what those controls are reacting to: a vessel that has lost its air, a leak, a valve letting water back, a setting, or a tank level. Which one depends on how the system is built and on the pattern of the cycling.
September 13, 2026 · 9 min read