Our rooftop water tank keeps overflowing onto the roof — is it the float valve, and how do I stop it wasting water?

Classic symptom, and you've guessed right — it's almost always the float (ball) valve. That valve is what's supposed to shut the incoming supply off when the tank reaches full; when it sticks, wears, or is set too high, water keeps filling past the line and pours out of the overflow pipe (which is doing its safety job — carrying the excess away so the tank doesn't burst).

A two-minute DIY check (tank access + safe roof only): open the lid and lift the float arm by hand. If the water stops, the valve mechanism is fine but set too high (bend/adjust the arm down so it shuts earlier) or the washer is worn. If it keeps running with the float lifted, the valve itself is worn/stuck and needs replacing — it's a cheap, standard part.

Why it matters — it's not just the bill: - Wasted water (and a rising DEWA bill), continuously. - Roof damp and waterproofing damage — constant water on the slab finds every weak point in the membrane and eventually shows up as a leak *inside*. - Structural load and standing water — and standing water on a roof is a mosquito-breeding and hygiene issue.

Other things to check: that the overflow pipe is clear and directed to a safe drain (not just onto the slab), and whether inlet pressure is so high it's forcing past the valve — a pressure-reducing valve can help there. A stuck float can also do the opposite — not fill at all — so it's worth knowing.

Since someone has to go up to the tank anyway, it's the sensible moment to have the float and overflow sorted and the tank checked/cleaned in one visit — a standard job for water tank cleaning in Dubai. Don't leave it running; the roof damage costs far more than the valve.