Low water pressure in Malta: pumps and roof tanks

Buyers arriving from the UK or northern Europe expect to open a tap and get mains pressure behind it. In Malta that is not how the plumbing is arranged. The mains feeds a tank on the roof, and the tank feeds the house. Everything about pressure in a Maltese dwelling follows from that one fact.

Why the tank is there

A roof tank is a buffer. It fills slowly from whatever the mains is doing and holds enough to run the house when the mains is doing very little. That decouples your shower from the network. It also means the pressure at your taps is no longer a function of the Water Services Corporation's pressure — it is a function of how high the tank sits above the tap, which for a top-floor bathroom is barely any height at all.

Gravity alone gives you about 0.1 bar for every metre of drop. A tank sitting a metre and a half above a top-floor shower head produces roughly 0.15 bar, which is enough to trickle and not much else. That gap is what the pressure pump exists to close. So the standard Maltese arrangement is three components working in sequence, and a fault in any one of them looks identical from the shower: no pressure.

The three parts

Float valve

The float valve is the mains side of the system. It sits inside the tank, opens when the level drops and shuts when the tank is full. It is the cheapest part of the installation and the most common source of the two classic complaints — a tank that never fills (valve stuck shut, or sediment in the seat) and a tank that never stops (valve stuck open, water running to the overflow, and a bill you will notice through ARMS).

The tank

Polyethylene is the normal material. Idroplast Manufacturing Malta lists roof tanks from 60 L up to 5,000 L, with prices quoted excluding VAT. Tower Hardware Store lists small tanks at the bottom of that range — a 100 L unit measuring 500 × 500 × 575 mm, and a 200 L — described as suitable for drinking water.

The practical constraint on size is rarely price. It is the roof. A 1,000 L tank weighs a tonne when full, sits on a slab you did not design, and has to get up there. In an apartment block the roof is usually common property and the condominium rules govern what may be placed on it and where. In a shell-form purchase, the tank is one of the items the buyer specifies and pays for, which is why it is worth deciding capacity before the first fix rather than after.

The pressure pump and its switch

The pump takes water from the tank and pushes it into the house. It needs to know when to run, and that is the job of a flow switch or a pressure switch. A flow switch senses water moving and starts the motor; a pressure switch senses the line pressure dropping below a set point and does the same. KHS Malta sells flow and pressure switches as separate line items, which matters: a pump that hums but never cuts in, or cycles on and off every few seconds, is usually a switch problem, not a motor problem, and the switch is the cheaper part.

What the hardware costs

These are counter prices for the goods. None of the four suppliers publishes a fitted price, so nothing here tells you what the installation costs — that depends on pipe runs, whether there is a dedicated electrical supply at the tank, and access to the roof.

Sizing by floors

The number that matters on a pump is the bar rating, not the wattage. Calleja publishes bar ratings against its STL Plus pressure and flow pumps, and that is the specification to compare between models.

Work it out in two parts:

1. Lift. Measure vertically from the pump to the highest outlet it has to serve. Every 10 metres costs 1 bar. A pump in a roof room serving a penthouse bathroom has almost no lift; a pump in a basement or at ground level serving a third-floor shower has around 10 metres and has spent a full bar before any water leaves the head.
2. Working pressure at the outlet. Add what you want to arrive with. A normal shower wants something in the region of 1 bar; a rain head or a multi-outlet arrangement wants more.

Two further points that catch people out. First, the rating is a headline figure — pumps deliver less pressure as flow increases, so a pump that just about satisfies one tap will disappoint two. Second, oversizing has a cost: more noise transmitted into the structure, more stress on old pipework, and shorter cycles on the switch.

For a typical two-storey Maltese house with the tank on the roof, the pump is fighting very little lift and is essentially there to supply working pressure. For a townhouse of three or four floors with the tank at the top, the lower floors are fine on gravity and the top floor is the problem — which is an argument for a pump close to the tank rather than one at the bottom of the building.

When a submersible well pump is the answer

Both KHS Malta and Calleja list submersible well pumps as a distinct category from booster and pressure pumps, alongside their bar ratings and prices. The distinction is where the pump sits. A pressure pump sits dry and pushes. A submersible sits in the water and lifts.

If the property has a well or a below-ground reservoir — common in older houses and in farmhouses in Gozo — the submersible is what gets that water up to the roof tank. It does not replace the pressure pump; it feeds the tank that the pressure pump draws from. A house can quite reasonably have both: a submersible in the well, a float valve on the mains as backup, and a pressure pump under the tank.

Practicalities before you order

• Shell form. If you bought in shell, none of this exists yet. Tank capacity, tank position and pump specification are your decisions and your budget line.
• Apartments. Roof access, tank siting and anything bolted to common parts fall under the condominium rules. Establish what is permitted before buying a 1,000 L tank.
• Gozo. Every tank and pump crosses on the ferry. None of the suppliers here publish Gozo delivery terms, so ask before ordering a bulky item.
• Hard water. Malta's water is very hard, and scale is the working environment for any pump, switch and float valve on the island. None of these sources quantify the effect on service life, but it is the reason a five-year-old switch behaves differently from a new one.