Underground Tank Cleaning in Riyadh

A ground cistern is the first stop for water arriving from the mains or from supply tankers, so it catches everything too fine to see: soft sand, dust, scale flakes and rust particles from older pipework. These settle layer on layer across the floor, and nobody notices them as long as the water sits still.

The catch is that the layer moves. Each refill hits the floor and kicks part of it up, and when the level drops the pump intake gets close to the deposit and draws grains up to the roof tank, strainers and mixers. That is why people complain of weak pressure or intermittent cloudiness without suspecting the floor of the cistern.

Over time the deposit consolidates from loose mud into a hardened mass in the corners and around the pump base. A quick rinse no longer works at that stage; it takes a proper solids pump and then hand scraping of the corners before the walls are washed.

• Cloudiness or sandy grains after each refill
• Lift pump draws air or runs louder than before
• Strainers and the roof-tank float clog repeatedly
• An earthy or stale smell when the lid is opened

A sealed cistern can be low in oxygen or hold stagnant gases with no smell at all, so entry never starts with simply lifting the lid and climbing in. The hatch is opened first and left to air out, fresh air is blown down to the floor, and the atmosphere is checked before anyone descends, with any engine exhaust kept well away from the opening.

The technician never goes down alone. A second person stays at the hatch to watch and communicate, a harness and line are used where needed, and low-voltage lighting suited to damp conditions replaces loose cable. A call-up and exit signal is agreed before the descent so nothing is left to guesswork.

Petrol or diesel engines are not run near the opening because their exhaust drifts into the tank, and the permanent lift pump is isolated electrically before work begins. Time inside is limited to what the scraping and washing require, and the technician comes out to refresh the air and returns when needed.

The level is drawn down with an ordinary transfer pump until only a thin film of water sits over the silt, then a solids pump that tolerates sand and grit takes over. The swap matters because a standard pump wears out and clogs quickly in mud. The layer is removed in batches, with the silt squeegeed toward the suction point instead of being left to settle in the corners.

Once the floor is clear, the corners, wall edges and the area around the pump base and ladder are scraped by hand, since hardened deposit collects there. The walls are then washed at controlled pressure with a suitable brush; excessive pressure or a wire brush can strip plaster or an old waterproof coat and open fresh pores.

The tank is rinsed from top to bottom until the outgoing water runs clear, and wash water is removed as it is produced to a discharge point agreed with the owner beforehand, so it does not flood the courtyard or reach a neighbour. The recovered silt is collected and taken away, not left to dry on site.

A full tank hides everything; an empty, washed one shows its condition. The technician checks walls, roof slab and floor for hairline cracks, damp patches, white salt bloom, flaking plaster, exposed or rusting reinforcement, and the state of any steel ladder rungs. The underside of the roof slab is looked at too, since dripping or heavy condensation there points to poor ventilation or damp coming from the courtyard.

The mechanical side is checked too: the foot valve and pump suction screen, the inlet pipe and level-control float, the overflow pipe and its screen, and how well the access cover and its frame seat. What is found on each item is noted, with photographs of the important spots for the owner to keep.

This inspection describes the condition; it is not a repair. If an active crack or outside seepage turns up, treatment follows once the cause is identified and is carried out on a fully dry surface. That is a different job, covered on the underground tank waterproofing page.

After the wash water is removed and the floor checked, the cover is closed and the cistern is refilled from the mains or a tanker. The first water often comes in hard, so the floor is watched to make sure it stirs up no leftovers, and the tank is allowed to fill gradually until the level reaches the pump intake.

The lift pump is not started until water covers its suction by a safe margin, because running dry or nearly dry damages it. Power is restored, the pump sound and roof-tank level are watched, and a far-away tap is opened to purge air and the first water from the line.

Slight cloudiness or air bubbles at first use are normal after the household lines have been drained and refilled. If cloudiness persists once both tanks are full and the lines have been flushed, the cause usually lies in the roof tank, the pipework or the strainers, not in the ground cistern.