Villas
Underground vs Rooftop Water Tanks in Dubai Villas
By the Dubai Water Tankers team · Published · Updated
What is the difference between the underground and rooftop water tank in a villa?
In most Dubai villas the underground tank is the main store, filled by the DEWA mains or a water tanker, and kept cool by the ground. A booster pump lifts water to a smaller rooftop tank, which feeds the taps by gravity. Tankers fill the underground tank; the rooftop tank refills itself from it.
- Underground tank = main store, filled by DEWA or a tanker
- Rooftop tank = smaller, fed by the booster pump
- Tankers fill the underground tank only
- Rooftop water heats up in summer; shade or insulation helps
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Street pressure in Dubai isn’t designed to push water up to the top floor of every home on demand. So most villas use a two-tank system:
- DEWA mains → underground tank. A float valve lets water in until the tank is full.
- Underground tank → booster pump → rooftop tank. The pump switches on when the rooftop tank drops.
- Rooftop tank → taps. Water flows down by gravity (some villas use a pressure pump instead of, or as well as, a rooftop tank).
The underground tank
- Job: main storage. It’s your buffer when the mains supply stops.
- Where: below the garden, driveway or side passage, under a manhole cover.
- Temperature: the ground keeps it cooler than the roof.
- Filled by: DEWA mains, or a water tanker through the same opening or a dedicated inlet.
This is the tank to know the size of. See villa water tank sizes.
The rooftop tank
- Job: short-term supply to the taps, by gravity.
- Where: on the roof, often plastic (GRP or polyethylene) or steel.
- Temperature: in summer, water in an unshaded rooftop tank can get very hot, which is why “cold” taps run warm in July and August.
- Filled by: the booster pump, from the underground tank. A tanker hose rarely reaches it, and it doesn’t need to.
Which one does a tanker fill?
The underground tank. The driver runs a hose from the truck to the tank opening or inlet and pumps the water in. Once it has water, the booster pump refills the rooftop tank automatically. If your pump was switched off while the tank was empty, turn it back on after the delivery.
Common problems and what they mean
| Symptom | Likely cause |
|---|---|
| No water anywhere, underground tank empty | Mains supply stopped; see no water in your villa |
| No water, underground tank full | Pump, pressure switch or valve |
| Water upstairs weak, downstairs fine | Rooftop tank low, or pump struggling |
| Water very hot from cold taps | Rooftop tank in direct sun |
| Rooftop tank overflowing | Float valve stuck open |
For pressure problems, see low water pressure in a Dubai villa.
Looking after both tanks
- Keep covers closed and sealed. Dust, insects and birds are the main sources of contamination.
- Have both tanks cleaned and disinfected by a qualified company, and plan the refill after cleaning.
- Shade the rooftop tank or use an insulated tank to reduce summer heat.
- Check the float valves occasionally; a stuck valve either overflows or never fills.
- Use sweet water only. Never put salt or site water in a home tank. Our sweet water tanker trucks carry sweet water only.