Drainage Lifting Stations and Sump Pumps
An explanation of how basements and low-level areas, which sit below the sewer, drain safely — by collecting waste in a sealed sump and pumping it up to the gravity sewer with float-controlled duty and standby pumps.
Drainage normally relies on gravity: waste flows downhill to the sewer. But many buildings have areas that sit below the level of the public sewer — basements, car parks, plant rooms, lower-ground toilets and lift pits. From these places, water and waste cannot fall to the sewer on their own; if nothing lifted it, it would simply collect and flood the lowest level.
A drainage lifting station (or sump pump system) solves this. It collects the low-level drainage in a pit, then pumps it up and over to a point where it can re-join the gravity sewer. This lesson explains how a lifting station is arranged, why it almost always uses two pumps, and how level controls and alarms keep it reliable.
How it works
Why lifting is needed. Any fixture or drain below the sewer invert cannot discharge by gravity. To drain a basement WC, a car-park gully or a plant-room floor drain, the waste must be raised to a higher level. The lifting station provides that lift, taking in drainage by gravity at the bottom and discharging it under pressure at the top.
The collection sump. Incoming drainage flows by gravity into a collection pit, or sump. For foul drainage this sump is sealed and vented to contain odours and gases, with the vent taken to a safe point. The sump gives the pumps a reservoir to draw from and sets the levels at which they start and stop.
Float switches and pump control. Level sensors — typically float switches — control the pumps automatically. As drainage fills the sump and the level rises, a switch starts a pump; as the pump empties the sump and the level falls, another switch stops it. This start/stop cycling keeps the sump from overflowing while avoiding the pump running dry.
Duty and standby pumps. Lifting stations almost always have at least two pumps: a duty pump that does the normal work and a standby pump that takes over if the duty pump fails or when inflow is unusually high. Controls usually alternate them so both share the wear, and a high-level alarm warns operators if the level keeps rising — for example if both pumps are overwhelmed or have failed.
The rising main and non-return valve. The pumps discharge into a rising main that carries the waste up to the gravity sewer. A non-return (check) valve on this line stops the lifted water from draining straight back into the sump when the pump stops. Once the waste reaches the higher gravity drain, it flows away normally to the sewer. For sensitive sites the system can also feed a building-management alarm so faults are noticed quickly.
Main types
In the UAE
- Many UAE buildings have basements and lower-ground levels below the public sewer, so foul and storm lifting stations are a common and necessary part of the drainage design.
- Foul lifting stations are sealed and vented to control odours and gases, and discharge connects to the municipal sewer in line with the relevant authority requirements.
- Reliability matters in a hot climate where a failed pump quickly causes backups and odours, so duty/standby pumps and high-level alarms — often linked to the building management system — are standard good practice.
How GPR applies this
GPR designs and installs drainage lifting stations and sump pump systems for basements, car parks and plant areas across Abu Dhabi as part of its MEP scope. GPR sizes the sump and duty/standby pumps to the inflow, arranges sealed vented pits for foul drainage, fits non-return valves on the rising main, and wires float controls and high-level alarms — often into the BMS — so below-sewer areas drain reliably without backups or odours.
Frequently asked questions
When is a lifting station needed?
Whenever fixtures or drains sit below the level of the public sewer — such as in basements, car parks and lower-ground plant rooms — because waste from there cannot reach the sewer by gravity.
Why do lifting stations have two pumps?
A duty pump handles normal flow and a standby pump takes over if the duty pump fails or inflow is unusually high; alternating them also shares the wear between the two.
What controls when the pumps run?
Float or level switches in the sump: a rising level starts a pump, and a falling level stops it, so the sump neither overflows nor lets the pump run dry.
What does the non-return valve do?
It stops the water the pump has just lifted from draining straight back down into the sump when the pump switches off, so the waste keeps moving up to the gravity sewer.
Why is a sewage sump sealed and vented?
Sealing contains the odours and gases from foul drainage, while a vent taken to a safe point lets the sump breathe as the level changes without releasing smells indoors.