WatchGas Last-O-More Tubing 3x5mm SST-3X5

Accurate gas sampling depends on what the tube is made of — not just what's coming through it.

The WatchGas Last-O-More Tubing 3x5mm is professional-grade sampling tubing for pump-drawn gas monitoring. Low-adsorption material means the atmosphere you sample and the atmosphere the sensor sees stay in agreement. Anti-tangle coating keeps deployment quick and predictable in the field. Sold by the meter — order the length you need for your sampling application.

Why tubing material matters for accurate gas sampling:

When you sample reactive gases through a length of tubing, the tube itself becomes part of the sampling system. Some tubing materials adsorb gas molecules on the way through — hydrogen sulfide, ammonia, sulfur dioxide, phosphine, and many volatile organic compounds all partially stick to standard silicone or common polymer tubing. On short sample runs, that adsorption produces false-low readings while the reactive gas is still saturating the tube walls. On repeated bump tests, adsorbed residual gas can bleed out of the walls of a previously-used tube and skew subsequent measurements.

Professional sampling tubing is engineered to minimize this adsorption behavior. Last-O-More is WatchGas's low-adsorption tubing line — engineered specifically to keep the atmosphere you sample and the atmosphere the sensor sees in as close agreement as possible. For OSHA 1910.146 permit-required confined space entry work, that agreement is the entire point of the atmosphere test.

Response-time delay: how tubing length affects your monitor reading.

Every meter of sampling tubing adds a fraction of a second to the sample response time — the time between when contaminated atmosphere enters the tube and when the monitor's sensor sees it. For short tubing runs (1–3 meters), the delay is negligible. For longer runs (7–10 meters, common for deep tank sampling), the delay becomes meaningful, and it matters for how you interpret bump-test timing, alarm response expectations, and evacuation lead time.

WatchGas specifies an effective maximum sample tube length of approximately 7.5 meters (25 feet) for the SST4-PUMP. Beyond that length, the sampling pump cannot reliably pull sample at the monitor's design flow rate, and readings can become unreliable. If you need longer sample runs than that, call PK Safety at 800.829.9580 — there are workarounds for extreme-reach sampling but they require adapting the monitoring workflow rather than just adding more tubing.

What this tubing is (and isn't):

• It IS professional-grade 3x5mm (3mm inner diameter, 5mm outer diameter) low-adsorption sampling tubing engineered for the WatchGas SST4-PUMP pump-drawn sampling workflow.
• It IS compatible with the WatchGas Ball Float (SST-BALL-FLOAT) — the ball float is designed to slip-fit over the intake end of this tubing.
• It IS part of the WatchGas SST4-PUMP sampling ecosystem alongside the SST-BALL-FLOAT (water-intake protection) and the SST-DFRPSV Demand Flow Regulator (calibration workflow).
• It is NOT for use with diffusion monitors (SST4-MICRO, SST4-MINI, SST1) — those monitors don't sample through a tube. They rely on ambient gas diffusion.
• It is NOT a substitute for proper atmosphere-testing procedure. Sample-line length, purge-time discipline, and periodic tubing replacement (recommended when contaminated or when switching between reactive-gas applications) still apply.

Key features:

• Low-adsorption material — minimizes gas molecule uptake by tube walls; more accurate readings for reactive gases (H2S, NH3, SO2, PH3) and VOCs
• Anti-tangle coating — quick deployment, less field frustration, safer sample-line handling at the mouth of a confined space
• 3x5mm dimensions — 3mm inner diameter, 5mm outer diameter; industry-standard small-bore sampling tubing
• Sold by the meter — order the exact length needed for your sampling application. Common lengths: 3m (utility vault entry), 5m (industrial tank entry), 7m (deep tank / max spec).
• Compatible with the WatchGas Ball Float (SST-BALL-FLOAT) — slip-fit connection at the intake end
• 2-year warranty
• Professional-grade at accessible pricing — $16/meter positions this tubing within reach of every SST4-PUMP owner, not just professional cal shops

How much tubing to buy:

• 1–3 meters: desktop calibration bench, short-reach sampling, general utility work
• 3–5 meters: standard confined-space entry (utility vaults, sewer, shallow tanks)
• 5–7 meters: deep tank entry (petroleum storage tanks, some wastewater applications, marine vessel holds)
• Maximum ~7.5 meters (25 feet): WatchGas specified upper limit for SST4-PUMP effective sampling. Longer runs risk unreliable pump performance.

Fleet operators typically buy in longer lengths and cut to specific job requirements — order a spool that covers your longest expected sample run plus a service margin.

PK Safety supports the full WatchGas SST4-PUMP sampling ecosystem — the ball float, the Demand Flow Regulator w/PSV (SST-DFRPSV), and this low-adsorption sampling tubing. For a complete sampling workflow order, or to talk through longer-than-standard sample runs, call us at 800.829.9580. Factory-trained technicians in-house for the full WatchGas SST platform. We also service BW/Honeywell (Factory Authorized Service Center), RKI, and RAE Systems monitors — one shop for a mixed-brand fleet's sampling infrastructure.

Part Number: WG01-411-0018-038 — WatchGas Last-O-More 3x5mm Sampling Tubing (sold by the meter, 2-year warranty)

Frequently Asked Questions

What makes Last-O-More tubing different from generic sampling tubing?

Two properties matter for professional gas sampling, and Last-O-More is engineered for both:

• Low adsorption — the tubing wall material minimizes gas molecule uptake as sample passes through. This matters most for reactive gases (H2S, NH3, SO2, PH3, some VOCs) that partially adsorb to standard silicone or generic polymer tubing. Adsorption produces false-low readings on short sample runs and can bleed carryover into subsequent readings.
• Anti-tangle coating — field-practical property. Sampling tubing that tangles in a bag or coil wastes time at exactly the wrong moment (pre-entry atmosphere testing when the crew is on the clock).

Together, these mean the atmosphere your monitor reads is closer to the atmosphere you actually sampled, and setup is faster and less frustrating.

How much tubing do I need for my sampling application?

Typical length guidance:

• 1–3 meters: desktop calibration bench, short-reach sampling, general utility work
• 3–5 meters: standard confined-space entry (utility vaults, sewer, shallow tanks)
• 5–7 meters: deep tank entry (petroleum storage tanks, some wastewater applications, marine vessel holds)
• Maximum ~7.5 meters (25 feet): WatchGas specified upper limit for SST4-PUMP effective sampling. Beyond this, the pump cannot reliably pull sample at the design flow rate.

Fleet operators typically buy longer lengths and cut to specific job requirements — order a spool that covers your longest expected sample run plus a service margin.

How does response time change with tubing length?

Every meter of sampling tubing adds a fraction of a second to sample response time — the delay between when the contaminated atmosphere enters the tube and when the monitor's sensor sees it. Rough guidance:

• 1–3 meters: delay is negligible for practical purposes; bump-test timing is essentially instantaneous
• 3–7 meters: delay is measurable (typically 3–10 seconds depending on pump flow rate); factor into bump-test timing expectations
• Beyond 7.5 meters: outside WatchGas SST4-PUMP specification. Pump flow may become unreliable, and delay compounds unpredictably.

For alarm response and evacuation lead time in continuous monitoring, be aware that a monitor at the end of a 7-meter tube is responding to atmosphere that entered the tube ~5–10 seconds earlier. In fast-changing atmospheres, that latency matters.

Does the Last-O-More tubing work with the WatchGas Ball Float and Demand Flow Regulator?

Yes. All three accessories are engineered as a coordinated sampling ecosystem:

• SST-BALL-FLOAT slip-fits over the intake end of this tubing to prevent water ingestion during wet confined-space entry
• The Last-O-More tubing itself carries the sample from the space to the monitor
• SST-DFRPSV Demand Flow Regulator uses the same 3x5mm tubing standard for cal gas delivery during bump tests and calibrations

Call PK Safety at 800.829.9580 for a complete sampling ecosystem quote covering all three accessories.

How do I cut the tubing to length and terminate the ends?

Cut with a sharp utility knife or dedicated tubing cutter for a clean square end. Avoid scissors or pliers — those tend to crush the tube and can cause a leak at the connection point.

Terminations depend on what's on each end:

• Intake end (going into the confined space): if you're using the SST-BALL-FLOAT, the ball float slip-fits over the tube end. Otherwise, leave the end square-cut.
• Monitor end: the tube slip-fits onto the SST4-PUMP sample port. Consult the SST4-PUMP manual for correct orientation and depth.

Store cut lengths in a clean container to keep debris from entering the tube walls between uses.

Do I need to replace tubing between different sampling applications?

Guidance depends on what you've been sampling:

• Between similar non-reactive sampling (e.g., LEL testing across multiple utility vaults on the same day): the same tubing is fine. Cleaning is optional.
• Between reactive-gas exposure and subsequent readings (e.g., after sampling an H2S-rich atmosphere): purge the tube by drawing clean air through it for 30–60 seconds before the next reading. If you've been exposed to high concentrations, consider replacing the tubing entirely — residual adsorbed gas can bleed out for hours.
• Between different reactive gases (e.g., H2S sampling followed by NH3 sampling): replace the tubing. Cross-contamination in reactive-gas sampling is difficult to fully purge.
• Periodically as preventive maintenance: replace tubing every 6–12 months of active use, or sooner if the tubing shows signs of contamination, discoloration, or physical damage.

Which WatchGas monitors is this tubing compatible with?

The Last-O-More 3x5mm tubing is designed for pump-drawn sampling on the WatchGas SST4-PUMP 4-Gas Detector — the only pump-drawn monitor in the WatchGas SST4 family.

It is NOT for use with the SST4-MICRO (diffusion), SST4-MINI (diffusion), or SST1 single-gas monitors. Those monitors don't sample through a tube — they rely on ambient gas diffusion to reach the sensors.

Ordering the full WatchGas SST4-PUMP sampling ecosystem, or planning a fleet-scale sampling deployment across multiple job sites? Call PK Safety at 800.829.9580. A person who knows the WatchGas SST platform and pump-drawn sampling workflow will pick up.