Hydraulic Elevator Explained: How Hydraulic Lifts Work

A hydraulic elevator, usually called a hydraulic lift in Singapore and the UK, raises its car by pumping oil into a cylinder that pushes the car or its sling upward. To descend, a valve lets the oil flow back to the tank and the car lowers under its own weight. It is one of the oldest forms of powered lift and remains a practical choice for low-rise buildings, goods lifts, car lifts and some homes.

This article explains how a hydraulic system works, the main arrangements, where hydraulic lifts suit and where they do not, what they demand of the building structure, and the safety and maintenance points owners should understand.

How a hydraulic elevator works

The system has three main parts. The power unit contains an oil tank, an electric motor and pump, and a control valve block. The cylinder and ram, also called the jack and plunger, convert oil pressure into lifting force. The car runs on guide rails in the shaft, just as in a traction lift, and is either seated on the ram or connected to it through a sling or ropes.

To go up, the motor runs the pump, forcing oil into the cylinder. The ram extends and the car rises. The valve block controls acceleration and deceleration so the ride is smooth and the car levels accurately at the floor. To go down, the motor stays off and the valve opens progressively, allowing the car’s weight to push oil back to the tank at a controlled rate. Because the lift uses energy only on the way up and has no counterweight, it uses more energy per trip than a counterweighted traction lift, though for a low-use lift the difference may be modest.

Direct-acting, holeless and roped arrangements

Direct-acting with an in-ground cylinder

In the classic arrangement, the cylinder sits directly beneath the car, extending down into a borehole in the ground as deep as the travel. The ram pushes up on the centre of the car. This is mechanically simple and gives a very smooth ride, but the buried cylinder must be protected against corrosion and leakage into the ground, and the borehole adds to construction work.

Holeless

Holeless systems place one or two cylinders inside the shaft, beside the car, standing on the pit floor. Telescopic cylinders with nested stages allow a reasonable travel without a borehole. This avoids drilling and makes inspection easier, though the travel is limited by the cylinder length.

Roped hydraulic

In a roped hydraulic lift the cylinder is mounted beside the car and carries a pulley at its top. Ropes pass over the pulley from a fixed point to the car, so the car moves twice as far and twice as fast as the ram. This increases the travel available from a given cylinder and is a common solution for slightly taller low-rise buildings.

Where a hydraulic lift suits

Hydraulic lifts are generally limited to low rises of a few storeys and moderate speeds. Within that range they have real strengths:

The main loads go to the pit floor, so the top of the shaft and roof structure carry little load.
The power unit can be located away from the shaft, often at the lowest level, giving flexibility where a roof machine room is unwanted.
Very heavy loads can be lifted smoothly, which suits goods lifts, car lifts and loading docks.
In an outage, the car can usually be lowered manually by releasing the valve, allowing passengers to be released at the lowest floor.

They are less suitable for taller buildings, intensive traffic and situations where energy efficiency is a priority. Heat from the power unit must be removed, and oil temperature affects ride quality. For a comparison with traction and other drives, see our overview of the types of lifts.

Hydraulic lifts in homes

In landed homes, hydraulic drives are one of several options alongside compact traction, screw-drive and pneumatic vacuum lifts. Their appeal is that the power unit can sit in a cupboard or store, and the shaft needs little headroom above the top floor. The pit, power unit space and oil heat are the main design issues. Our guide to the home lift in Singapore covers the practical and approval aspects of adding a lift to a house.

What the structure has to carry

A hydraulic elevator puts its loads where a traction lift does not. The ram reaction, including the car, its rated load and dynamic effects, is transferred to the pit floor or, for in-ground cylinders, to a supporting beam or base at the bottom of the shaft. The pit slab and its foundations must be designed for this concentrated load, along with buffer reactions in an overrun. For holeless and roped systems, cylinders and their supports may also introduce loads into the shaft walls through brackets.

Guide rails transmit lateral forces from the car into the shaft walls at their bracket points, and the walls must accommodate these. The pit must be dry, because oil and water do not mix well with electrical components, and waterproofing below ground is critical in Singapore’s high water table and heavy rainfall. In an existing building, a new pit may need excavation near existing foundations, which must be checked. These are routine matters for a structural engineer, but they need to be resolved with the lift supplier’s actual loads, as described in our article on types of structural loads.

Safety devices, maintenance and regulation

Hydraulic lifts have their own set of safety devices. A rupture valve on the cylinder closes automatically if the oil flow suddenly increases, as it would if a hose burst, stopping the car from falling. Pressure relief valves limit the maximum pressure in the system. Anti-creep devices re-level the car if oil slowly leaks back and the car settles below floor level. Manual lowering valves allow a trapped car to be lowered safely in a power failure, and there are electrical safety circuits on doors and overtravel just as on any lift.

Maintenance focuses on oil condition and level, hoses and seals, cylinder packing, valve settings and the power unit. Leaks should be traced and repaired promptly. In Singapore, lifts are regulated by the Building and Construction Authority as fixed installations under the Building Control Act and the Building Control (Fixed Installations) Regulations 2025, which took effect on 1 October 2025. Owners must engage BCA-registered contractors for installation and maintenance, keep to the prescribed maintenance frequency and, where a Permit to Operate is required, have the lift examined and tested annually in the presence of an independent specialist. Our article on lifts and escalators explains the framework.

Frequently asked questions

How high can a hydraulic elevator go?

Hydraulic lifts are generally used for low-rise buildings of a few storeys. The travel is limited by the cylinder length, the stability of the ram and the energy needed to pump oil. Roped hydraulic arrangements extend the travel, but for taller buildings a traction lift is the usual choice.

Is a hydraulic lift safe?

Yes, when properly designed, installed and maintained. A rupture valve prevents the car from falling if a hose fails, relief valves limit pressure, and the car can be lowered manually in a power failure. Regular maintenance by a registered contractor keeps these devices working.

Does a hydraulic lift need a machine room?

It needs space for the power unit, which contains the tank, pump, motor and valves, but this can usually be located at the lowest level near the shaft rather than above it. The space needs ventilation to remove heat and access for maintenance.

What is the difference between a hydraulic and a traction lift?

A hydraulic lift pushes the car up with an oil-driven ram and lowers it under gravity. A traction lift hangs the car from ropes over a motor-driven sheave, balanced by a counterweight. Traction lifts suit taller buildings and use less energy, while hydraulic lifts suit low rises and heavy loads.

Why do hydraulic lifts sometimes sink below floor level?

Small internal leakage past valves and seals can let the car settle slowly when stationary, and changes in oil temperature affect volume. Anti-creep systems re-level the car automatically. Persistent sinking indicates a fault that should be checked by the maintenance contractor.

Planning a lift pit, shaft or new lift in an existing building? Talk to our consultancy or get in touch.