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Australia application guide · 2026-11-12 · ELEHPD

Float Valve vs Float Switch for Stock Troughs & Rural Water Tanks (Australia)

A decision guide for rural installers, irrigation wholesalers and pump shops: when a mechanical float valve is the right part for a stock trough, and when the job actually calls for an electrical float switch.

Walk into any Australian rural supply store and you will find troughs, floats and valves racked together, which is why the two parts are so often specified for each other's job. They are not interchangeable. One is plumbing that stops water; the other is an electrical input that tells a pump, solenoid or alarm what to do. On a bore-fed property with a header tank several hundred metres from the trough, choosing wrong means a dry trough, a burnt-out pump, or a tank overflowing into a paddock. This guide sets out the deciding questions for 230/240 V rural systems and the spec details worth putting on an RFQ.

1. The difference in one sentence

A mechanical float valve is a valve: a buoyant arm rises with the water and physically closes an inlet orifice. It needs no electricity, no cable and no controller; it simply meters flow to hold one level in one vessel. A cable float switch is a sealed electrical contact: a moulded body with a steel ball and a microswitch tilts as the level changes and opens or closes a circuit. It moves no water at all — it switches a pump, a contactor coil, a solenoid or an alarm. Because it produces a signal, a single switch can protect a bore pump, and two or three can co-ordinate a tank, a trough and a high-level alarm.

That distinction drives everything else: the valve answers "is this trough full?", the switch answers "should this pump be running?".

2. When a float valve is genuinely the right answer

There are three rural cases where a valve is still the simplest, most robust choice:

Gravity or mains-fed troughs. Water arrives under its own pressure from a header tank or a scheme line, and there is no pump to control. The valve closes the inlet as the trough fills.
No power at the point of use. A remote paddock trough with no 240 V run — common on larger properties and on solar-only setups — has nothing for a switch to talk to.
One level, one vessel, no telemetry. A single concrete or poly trough where the only requirement is "don't overflow". A valve does that cheaply with no wiring and no electrician.

Keep the valve in these cases. It is also worth retaining as a mechanical backup even on a switched system: if a controller or contactor fails, a valve can still stop the trough overflowing. Rural resellers commonly stock both parts for exactly that reason.

3. When you must move to a float switch

As soon as water has to be pumped, or someone needs to know the level, a valve is no longer sufficient. Typical triggers on Australian properties:

Bore/artesian to header tank. A bore pump fills a header tank that gravity-feeds the troughs. A high-level float in the header stops the pump when full; a second low-level float cuts it before the bore runs dry.
Dry-run protection. A valve in the trough cannot see the source. A low-level float in the source or header tank can, and prevents the pump from sucking air and cooking the seal — the single most expensive failure in a remote pump setup.
High-level alarm / overflow. An independent alarm float gives a signal to a buzzer, a dialler or a remote-monitoring input. Increasingly relevant where rural systems add telemetry and solar pumping.
Multiple tanks and troughs. Two or three floats with a controller co-ordinate filling across tanks; one mechanical valve per trough cannot.

For the electrical background see our rainwater tank float switch guide (mains changeover and overflow logic), and for dirty-water duty the septic & AWTS float switch guide.

4. 240 V wiring, contactors and AS/NZS 3000

Australian rural pumps are mostly single-phase 240 V / 50 Hz, with three-phase 415 V on larger bore and irrigation sets. A float switch may switch a small pump directly only where its contact rating comfortably exceeds motor inrush — our UKY series is offered in 10 A (8 A) and 16 A (8 A) versions at 250 V AC, with 380 V maximum isolation. For anything larger, or any three-phase set, the float should be a signal into a contactor so the float contacts carry only the coil current. All fixed wiring follows AS/NZS 3000 (the Wiring Rules), is done by a licensed electrician, and has RCD protection as required. Keep float leads in conduit and away from the pump power cable.

Where a solar or telemetry system runs a 12/24 V DC control loop, keep that low-voltage circuit electrically separate from the 230/240 V pump circuit. A float rated for 250 V AC does not by itself make the whole installation compliant — it is one component in a system the installer signs off. If a trough is fed from a potable supply, ask us for material data and have the installer confirm the applicable materials requirement (for example AS/NZS 4020); a float switch is a control component, and ELEHPD does not claim WaterMark certification for its floats.

5. Specs that matter on a rural RFQ

Rural duty is harder than a clean indoor tank: stock bump the fittings, troughs carry silt and algae, cables sit in sun and frost, and sites are far from a spare part. Specify from real ratings, not a generic "float switch":

Cable length: standard factory lengths 2 / 3 / 5 / 10 / 15 m. Order enough to reach the controller with slack for the trip angle; a polypropylene counterweight slides on the cable to set the switching level without tools, so one cable length can serve several set-points.
Sealing and temperature: IP68CS for permanent immersion, rated 0–70 °C (working range to 80 °C), suitable for clean water, wastewater and mild acid/alkali.
Endurance: over 100,000 mechanical cycles and over 50,000 electrical cycles — the number that matters when a bore pump starts dozens of times a day.
Body and cable: moulded polypropylene float with PVC or HO7RN-F flexible cable; a 3-core black / blue / brown lead gives both pump-down and pump-up wiring from the same float, and NO/NC selection should be stated on the order.
Physical protection: mount the float where stock cannot chew or snag the cable, use a strain-relief at the tie-off, and keep the cable out of the trough's traffic path. A counterweight that can be moved without tools makes seasonal level changes straightforward.

All figures above come from our published UKY series specifications; if a project needs a different rating, cable jacket or contact arrangement, ask for the datasheet rather than assuming the standard build fits.

6. A decision checklist for resellers and installers

Is the trough fed by gravity/mains pressure, or by a pump? No pump → valve. Pump → switch.
Is there power at the control point, and is it 240 V single-phase, 415 V three-phase, or a 12/24 V DC solar loop?
Which jobs are needed: fill/stop, dry-run cut-out, high-level alarm, or all three? Count the floats separately.
Where does each float sit (header tank, source, trough), and what cable length reaches the controller?
Will a licensed electrician wire it under AS/NZS 3000, and is a contactor needed for the motor inrush?
Are potable-water materials or any approval requirements to be confirmed by the plumber/specifier?

Keep a mechanical valve in the bill of materials as a backup on any switched trough system. It is a cheap second line of defence when a contactor sticks or a float cable is damaged by stock.

FAQ

Can I use a float switch instead of a float valve in a stock trough?

Not as a drop-in replacement. A mechanical float valve physically shuts off the water flow into the trough and needs no power; a cable float switch only makes or breaks an electrical circuit, so it needs a pump, solenoid or contactor to act on. If your trough is gravity or mains fed with no pump, keep the valve. If the water is pumped from a bore or a header tank, fit the switch to control the pump and use the valve only as a mechanical backup.

What stops a bore pump from running dry when the header tank empties?

A low-level float switch in the header tank wired as a pump-down or pump-up interlock cuts the pump before it sucks air. A float valve in the trough cannot do this, because it only sees the trough level and has no electrical output. Specify a second, independent float for dry-run protection rather than asking one float to do both start/stop and low-level cut-out.

Does a float switch need WaterMark certification in Australia?

A float switch is an electrical control component, not the plumbing assembly. WaterMark requirements apply to the complete plumbing installation and are determined by the plumber or specifier and the local authority. ELEHPD does not claim WaterMark certification for its float switches; for troughs fed from a potable supply, ask us for material data and confirm the materials requirement (for example AS/NZS 4020) with the installer.

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Supplying the Australian market

ELEHPD manufactures and wholesales float switches and level controllers to distributors, rural and irrigation wholesalers, pump packagers and OEMs. For the Australian market we supply factory-direct with English datasheets and labelling, OEM/private-label options, and short lead times — spares and documentation are supplied from the factory, not from a local warehouse. See our Australia market page for voltage, standard and application notes.

Talk to us about your specification

Send the source (bore, header tank or mains), the pump rating, the control jobs you need and the cable run, and we will confirm the closest match from the ELEHPD catalogue, the documentation available for it and the lead time. OEM branding and buyer-specific cartons are available on qualified volumes.

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