Float Valves

Automatic level control in tanks, cisterns and basins. The float rises and falls with the liquid, opening and closing the supply without electrical power or manual intervention.

How float valves work

Float valves are automatic level control devices that require no electrical power, sensors or control logic. A float connected to a lever arm follows the liquid level in the tank: when the level drops, the float drops and the lever opens the supply valve; when the level rises to the set-point, the float lifts the lever and closes the valve.

The principle is simple and reliable, used for centuries: the hydrostatic buoyancy of the liquid on the float provides the driving force for opening and closing. Modulation is automatic: the valve opens proportionally to demand, maintaining a stable level even with variable consumption.

Roffia distributes float valves in brass for potable and industrial water and in stainless steel for food, chemical and high-temperature applications. Available models include lever arm with plastic or metal ball, and pilot-operated high-capacity versions for large tanks and cooling towers.

Float valves for tanks — Roffia srl

Lever arm and ball valves

  • Spherical float in plastic or stainless steel
  • Adjustable arm length
  • Body in brass or stainless steel
  • DN 10–50, pressure up to PN 16
  • Ideal for small to medium tanks
  • Side or top mounting

Pilot-operated (high capacity)

  • Pilot float separate from main valve
  • High-capacity main valve
  • DN 50–150, flow up to 200+ m³/h
  • Fine adjustment of shut-off level
  • Cooling towers, industrial tanks
  • Robust construction, low maintenance

Technical specifications

  • DN: 10–150 mm (3/8"–6")
  • PN: 6, 10, 16 bar
  • Temperature: up to 80 °C (120 °C stainless)
  • Connections: BSP threaded, flanged
  • Materials: brass, bronze, stainless AISI 316
  • Floats: PP, PE, stainless steel

Typical applications

Water storage tanks and cisterns

Float valves are the standard solution for maintaining the level in water storage tanks, pressure sets, underground and overhead cisterns, and lift stations. They guarantee automatic filling without risk of overflow, without need for electrical control and with minimal maintenance.

Cooling towers

Evaporative cooling towers continuously lose water through evaporation and blowdown. Pilot-operated high-capacity float valves automatically replenish lost water, keeping the basin level within safe limits. Roffia supplies specific valves for cooling towers with pressures up to 6 bar.

Livestock watering and agriculture

For automatic watering troughs in stables, piggeries and poultry farms, stainless steel or food-grade plastic float valves ensure fresh water is always available without waste. Compact and robust models withstand intensive use and animal presence.

Industrial processes

Process tanks, galvanic baths, surface treatment plants, washing and cooling circuits in the manufacturing industry. For chemical fluids, stainless steel 316L or PTFE-lined versions are available with corrosion-resistant floats.

Roffia float valve range

Standard brass
DN 10–50, domestic water
Stainless steel
DN 10–40, food and chemical
Pilot-operated high capacity
DN 40–150, cooling towers
Compact ball type
For small tanks
With check valve
Integrated backflow prevention
Adjustable arm
Customisable level
Bottom entry
Bottom-of-tank mounting
Spare kits
Floats, seals, levers

Frequently asked questions

What is the difference between a lever float valve and a ball float valve?
Traditional lever float valves use a float mounted on a lever arm that rises and falls with the liquid level, actuating a needle or gate valve to close or open the supply. Ball float valves use a hollow sphere (stainless steel or plastic) that floats directly on the liquid and, through a lever mechanism, operates the plug. The principle is the same, but ball versions are more compact and suited to smaller tanks. For large industrial tanks and cooling towers, long-arm floats with more precise modulation and higher flow rates are preferred.
How do I size a float valve for a tank?
Sizing depends on: (1) Required fill flow rate — the valve must deliver a flow equal to or greater than maximum anticipated consumption; (2) Supply pressure — determines the DN and Kv needed to achieve the flow; (3) Shut-off level — the float must close completely before the tank overflows, with a safety margin; (4) Materials — based on the fluid (potable water, cooling water, chemical fluids). For cooling towers and industrial vessels, Roffia recommends pilot-operated high-capacity valves with fine adjustment of shut-off level.
Can I use a float valve for hot water or steam?
Standard brass float valves with rubber seals are suitable for cold water up to 60–80 °C. For hot water from 80 to 120 °C, stainless steel models with PTFE or high-temperature EPDM seals are required. For condensate and steam systems, conventional float valves are not used — instead, float-type steam traps are employed, designed to withstand steam temperatures and pressures and automatically separate condensate from live steam. Roffia can advise the correct solution for your service.
What are pilot-operated float valves and when are they used?
Pilot-operated float valves separate the level sensing function (handled by a small pilot float) from the shut-off function (handled by a large main valve). When the level drops, the pilot opens a control line that depressurises the chamber above the main plug, allowing it to open under line pressure. When the level rises, the pilot closes and pressure re-closes the main plug. Advantages: very high flow rates (hundreds of m³/h), fine adjustment of shut-off level, no external lever. They are used in large cooling towers, process tanks and water treatment plants.
How often should a float valve be inspected?
Maintenance depends on water quality and service conditions. Generally: (1) Six-monthly visual inspection — check that the float is not punctured or encrusted, that the arm moves freely and that there are no leaks with the valve closed; (2) Annual cleaning — remove limescale, algae and sediment from seat and plug; (3) Seal replacement — every 3–5 years or at the first sign of leakage. For very hard water or fluids with suspended solids (evaporative towers), more frequent maintenance may be necessary. Roffia supplies original spare kits for all float valves in our catalogue.

Request a float valve quote

Please provide tank type, required flow rate, supply pressure and fluid. We will recommend the most suitable valve and send a prompt quotation.

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