How do I select the correct siphon tube length?

Measure the internal height of the extinguisher cylinder from the valve seat to the base. Subtract 5–10 mm—the tube should reach close to the bottom without touching it. Most manufacturers publish a cylinder-model-to-tube-length cross-reference table; request one from your supplier.

What happens if the siphon tube is too short?

A short tube creates a dead volume of agent at the bottom of the cylinder that cannot be discharged. The extinguisher will run out of agent prematurely, reducing its effective fire rating and potentially leaving the operator without suppression when it matters most.

Can I use an aluminium tube in a water extinguisher?

Aluminium corrodes in contact with water over time, especially if the water is not deionised. HDPE is the correct material for water, foam, and wet chemical extinguishers. Always match the tube material to the agent type.

How do I check for internal blockage?

Hold the tube up to a light source and look through it—you should see a clear, unobstructed bore. For opaque HDPE tubes, pass a flexible wire or pipe cleaner through the full length. Any resistance indicates caking or debris that warrants replacement.

Why does the tube crack at the valve connection?

Repeated vibration, rough handling during transport, and over-tightening during assembly are the common causes. Aluminium tubes are particularly susceptible to fatigue cracking at stress risers near the press-fit or threaded section. Inspect this area carefully during every refill.

Can I reuse a siphon tube from a discharged extinguisher?

Only if it passes visual inspection (no cracks, bends, or blockage) and the valve connection is still tight. Given the low cost of replacement tubes, many workshops adopt a blanket replacement policy at every refill for quality assurance.

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Siphon Tube / Dip Tube – Aluminium & HDPE (Multi-Size)

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Product Details

MaterialsAluminium alloy (powder) / HDPE (liquid agents)

Tube Outer Diameter8–12 mm (varies by model)

Standard Lengths200 / 300 / 400 / 500 / 650 mm

End FittingPress-fit or threaded (valve-specific)

Application – AluminiumABC / BC dry powder extinguishers

Application – HDPEWater / foam / wet chemical extinguishers

Max Working Pressure25 bar (aluminium) / 20 bar (HDPE)

PackagingBundle of 10 / 25 / 50 pcs per length

Custom CuttingAvailable for non-standard cylinders

Extinguisher Replacement Parts

Siphon Tube / Dip Tube – Aluminium & HDPE (Multi-Size)

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Description

The siphon tube (also called a dip tube or pick-up tube) is the internal conduit that channels the extinguishing agent from the bottom of the cylinder up to the valve and out through the discharge hose. Without it, pressurised gas would simply vent out the top of the cylinder, leaving the powder, foam, or water sitting uselessly at the bottom. It is one of the simplest yet most failure-critical components in any stored-pressure extinguisher.

Siphon tubes are manufactured in two materials: aluminium alloy (for dry chemical powder extinguishers) and high-density polyethylene (HDPE) (for water, foam, and wet chemical extinguishers). Aluminium tubes are lightweight, corrosion-resistant against MAP and bicarbonate powders, and rigid enough to maintain alignment inside the cylinder during handling and transport. HDPE tubes are chemically inert against aqueous agents, flexible enough to curve around internal components, and immune to galvanic corrosion.

The tube length must be precisely matched to the cylinder height. It should reach within 5–10 mm of the cylinder base to ensure near-complete agent pickup—a tube that is too short leaves a dead volume of un-dischargeable agent at the bottom, reducing effective capacity. A tube that is too long bottoms out, bends, and may crack at the valve connection. Most manufacturers supply siphon tubes in standard lengths (200 mm to 650 mm) keyed to common cylinder models; custom cutting is also common in high-volume refilling workshops.

The top end of the tube press-fits or threads into the valve body. The seal at this joint is critical: a loose or cracked connection allows pressurised gas to bypass the agent and vent directly, producing a spectacular but useless discharge of pure nitrogen with no firefighting capability. During every refill, the tube must be visually inspected for cracks, bends, internal blockage (powder caking is the #1 culprit), and secure valve connection.

Replacement siphon tubes are inexpensive, so the maintenance rule of thumb is simple: if in doubt, replace it. A blocked or cracked tube that goes undetected during refilling will produce a non-functional extinguisher—a liability nightmare for the service provider and a life-safety hazard for the end user.

Tubes should be stored vertically in a clean, dry environment to prevent bowing. Aluminium tubes should not be stored in contact with dissimilar metals to avoid galvanic corrosion. HDPE tubes should be kept away from direct sunlight and heat sources that could cause softening and permanent deformation.