TECTULby IMR

Fluid conveyance · Plastic float valves

TECHNICAL DATA SHEET

FT-TC-VAL-FLOTADORA-PVC-001

Issue date: August 4, 2026 · Rev. 001

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Plastic-body float valves: PVC lever type and automatic piston type

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This sheet covers the two plastic-body float valves in the TECTUL catalog, which share material but not mechanism. The PVC float valve (1/2″ to 2″ NPT, 5 variants) is a classic lever valve with an external float; the automatic float valve, in food-grade PA66 nylon, is an internal-piston valve actuated by the line's own pressure, with a washable stainless filter and no external arm. That is why the first is described by a maximum pressure per float size and the second by a continuous working-pressure range. For the PVC line, this sheet publishes the most complete manufacturer data in the whole catalog float valve family: the survey of the LD-856A model with flow rates by pressure, maximum pressure per float size, materials per component and the complete dimensional table from drawing LD-85SA.

SKU VT-59214 (PVC float valve, 1/2″-2″ NPT, 5 variants) · plastic block of 2 references; the second is the automatic float valve in food-grade PA66 nylon, 1/2″ male BSP thread with DN25 port

1. Technical specifications: 2 plastic references and the LD-856A manufacturer data

The TECTUL catalog publishes two plastic-body float valves. They share the material's rationale —they do not corrode in water with chlorine, fertilizers or chlorides, where bronze and brass are attacked— but they do not share a mechanism, and therefore they do not share the way their capacity is declared (section 2). This family has no single international rating standard: each manufacturer declares its own.

1.1 Plastic-body references in the TECTUL catalog

The PVC float valve publishes 5 variants: there is no 1-1/4″ or 2-1/2″ in the active series. The 0-120 °C thermal range of the automatic float valve is catalog data from that product's manufacturer and corresponds to the PA66 compound; it does not apply to the PVC-U body of the first reference, whose ceiling is 60 °C (140 °F) like the rest of TECTUL's plastic catalog (FT-TC-VAL-PIE-PVC-001 and FT-TC-ACC-PVCP-001, not repeated here). Metal-body float valves (bronze, brass, stainless) and the kit spare parts are not in this sheet: they are in FT-TC-VAL-FLOTADORA-METAL-001.

1.2 Manufacturer data: PVC float valve, LD-856A line

In August 2026 TECTUL compiled the complete commercial data sheet for the PVC float valve from the manufacturer LD Pipe Fittings & Valves (Taiwan), model LD-856A, from the commercial catalog and the manufacturer drawing LD-85SA. It is the most complete performance data in the whole catalog float valve family and serves as the engineering reference for the «PVC float valve» line.

1.3 Dimensional table of the LD line (manufacturer drawing LD-85SA, mm)

Dimensions in millimeters. Di and Do are the connection diameters, L the overall length, H the height, and S and W arm dimensions. Threads per size available in NPT and BSPT (for example 1″-NPT-11.5 and 1″-BSPT-11). The manufacturer drawing's table covers 1/2″ to 3″; the series published by TECTUL under «PVC float valve» runs 1/2″ to 2″ (5 variants) — the exact correspondence between each catalog variant and its drawing row is confirmed on quotation. Source: manufacturer drawing LD-85SA and commercial catalog LD-856A from LD Pipe Fittings & Valves, compiled by TECTUL in August 2026; these are manufacturer data, not independently tested by TECTUL.

2. Two different mechanisms under the same commercial name

The two references in this sheet are sold as «float valves», but they work in incompatible ways. Confusing them when specifying produces the block's most expensive error: asking for a pressure range where there is only a closing point, or expecting an external arm where there is none.

When each one applies

The PVC lever float valve is the option when the tank has room for the arm and float, when the actuation level should be visible and adjustable by hand, and when the required size exceeds 1/2″. The automatic piston valve is the option when there is no room for an arm, when line pressure is highly variable (its 1.5 to 150 psi range covers everything from a gravity tank to a high-pressure line), when the water carries particles worth filtering before the seat —it has an integral washable stainless filter— and when the material requirement is food grade, which is what the PA66 nylon provides.

3. Enlarging the float raises the rating without touching the seat

3.1 The manufacturer figure that reveals the physics

The LD-856A data sheet publishes two ratings for the same valve: 100 psi with a 6″ float and 150 psi with an 8″ float. What is notable is what does not change between the two configurations: neither the connection size, nor the seat, nor the rod —8″ in both cases—. The manufacturer raises capacity by 50 % by enlarging the float alone.

The reason is a moment balance. In a lever float valve there are two opposing forces:

• The closing one: the float's buoyant thrust —proportional to its volume, and a sphere's volume grows with the cube of the diameter— multiplied by the lever arm ratio. Going from a 6″ float to an 8″ one multiplies the volume by about 2.4.
• The one to overcome: line pressure multiplied by the seat area, which grows with the square of the seat diameter.

Since the manufacturer leaves the seat untouched and only enlarges the float, the entire gain goes to the closing-force side. Hence the jump from 100 to 150 psi.

3.2 Confirmation from the other direction

The same physics is observed in reverse in the metal line documented in FT-TC-VAL-FLOTADORA-METAL-001: there the manufacturer Helbert, with the standard copper-ball kit, publishes 125 psi at 1/2″-3/4″, 150 psi at 1″-1-1/2″ (scaling the kit with the size) and stops publishing a figure from 2″ to 3″, where the seat is already too large for the standard float. One series raises the rating by enlarging the float; the other stops publishing it when the seat wins the race. These are two independent manufacturer catalogs behaving exactly as the moment balance predicts.

3.3 What to do with that when specifying

The relationship between float size, arm length, seat area and closing pressure is a standard consequence of solid mechanics and fluid statics, illustrated here with two real manufacturer data series. It does not come from testing by TECTUL nor does it constitute a selection formula: an actual unit's performance depends on the exact assembly, the seal condition and the manufacturing lot.

4. Mounting, maintenance and distinction from toilet fill valves

4.1 Mounting the PVC lever float valve

• Horizontal, with the body passing through the tank wall above the maximum level and the arm inward. The discharge must sit above the water level, never submerged.
• Arm and float free throughout their travel: without rubbing the tank wall, other piping, the ladder or the body itself. A single point of contact leaves the closure incomplete and the valve dripping permanently. With the 8″ float configuration, verify the space before purchasing.
• Plastic thread: hand-tight plus 1 or 2 turns with a wrench, with PTFE tape or a PVC-compatible sealant. Over-tightening is the number-one cause of plastic thread failure. In a transition to metal, the plastic male always goes inside the metal female, never the reverse. Wrench on the body, never on the arm or the float.
• Rod-to-float and rod-to-arm joints: hand-tight only, per the LD line manufacturer's guide; they are not wrench-tightened.
• The closing level is adjusted by changing the float's position on the rod. Bear in mind that this geometry also defines the closing force (section 3): an aggressive adjustment can leave the valve unable to close against the line.

4.2 Mounting the automatic piston float valve

It is compact and requires no arm travel. It threads in by its 1/2″ male BSP end; the flow port is DN25. It comes with a washable stainless steel filter at the inlet: provide access for removing and cleaning it, because a clogged filter reduces flow and ultimately prevents the piston from operating. The BSP thread is not interchangeable with NPT without an adapter: verify before installing.

4.3 Maintenance and diagnosis

4.4 Distinction: these are not domestic toilet fill valves

The two references in this sheet are for storage tanks, cisterns, reservoirs and industrial, agricultural and process applications, with 1/2″ to 2″ connections and bodies in PVC-U or PA66 nylon. Domestic toilet fill valves are a different category: a miniature internal float or sliding-cup mechanism, sized for a toilet tank, with a different connection, a different body and a different flow rate. They share the physical principle of float closing, but they are not interchangeable in application, size or catalog. Ordering one for the other is this category's most frequent purchasing error.

5. Frequently asked questions

How much flow does a PVC float valve deliver?

Per the LD-856A line manufacturer's catalog data: 47 GPM (178 L/min) at 30 psi and 61 GPM (231 L/min) at 60 psi. Flow rises with line pressure, it is not a single value: to size a tank's filling time you must start from the actual pressure available at the point.

How much pressure does the PVC float valve withstand?

It depends on the float size, not on the body: 100 psi (6.9 bar) with a 6″ float and 150 psi (10.3 bar) with an 8″ float, with the same 8″ rod and the same seat. If the line at the installation point runs above 100 psi, the applicable configuration is the 8″ float, first verifying that the tank has room for the larger float's travel.

Why does a larger float withstand more pressure?

Because the force closing the valve comes from the float's buoyant thrust —proportional to its volume, which grows with the cube of the diameter— multiplied by the lever arm ratio, while the force to overcome is pressure times the seat area. Enlarging the float without touching the seat sends the entire gain to the closing side. It is the same physics that explains, in reverse, why the bronze line manufacturer stops publishing a closing pressure from 2″ upward (FT-TC-VAL-FLOTADORA-METAL-001).

What is the difference between the PVC float valve and the «automatic» one?

They are different mechanisms. The PVC float valve closes by lever with an external float: hence its figure is a maximum pressure point per float configuration. The automatic one is an internal-piston valve actuated by the line's own pressure, with no visible arm or float: hence it publishes a continuous working pressure range (1.5 to 150 psi), comes in food-grade PA66 nylon, carries a washable stainless filter and is available only in 1/2″ BSP with a DN25 port.

Does the automatic float valve work on a gravity tank?

Only if at least 1.5 psi (0.1 bar) of pressure is available, roughly one meter of water column. Below that minimum the piston has nothing to operate with. If the system is pure gravity at low head, the right mechanism is the lever float valve, which does not depend on line pressure to close.

Does it work for a toilet tank?

No. These two references are for storage tanks, cisterns and industrial, agricultural or process applications, with 1/2″ to 2″ connections. Domestic toilet fill valves use a miniature internal float mechanism with a different body, connection and flow rate: they share the physical principle, not the application, and they are not interchangeable.

PVC or bronze for the tank float valve?

PVC when the water has tank chlorine, fertilizers or chlorides that attack copper alloys, and when weight matters. Bronze when the service is clean fresh water, permanent and mechanically demanding, and when a closing pressure backed by the manufacturer's table at sizes 1/2″ to 1-1/2″ is required (FT-TC-VAL-FLOTADORA-METAL-001). For potable water with a material requirement or the food industry, no copper alloy applies: the food-grade PA66 nylon of the automatic valve or a stainless body is required.

6. Application notes

7. Technical notice and limitation of liability