Double Containment Is More Than Two Pipes
Putting one pipe inside another is the beginning of the engineering — not the finished solution. The annular space is its own system.
The Annular Space Is a Functioning System
Supports
The annular space carries its own load path, distinct from the carrier pipe's support requirements.
Expansion allowance
Carrier and containment pipe expand at different rates under the same temperature swing — the annular space has to accommodate both.
Drainability
If the primary pipe leaks, the fluid has to go somewhere specific, not pool at a random low point.
Leak detection
Discrete-point or continuous-cable — the method has to match the consequence and the geometry.
Inspection access
A system nobody can physically inspect isn't really monitored, just installed.
Low points
Engineered drain locations, not incidental ones created by however the run happened to be installed.
Termination points
Where the double-contained run ends has to be as deliberately engineered as where it starts.
Penetrations
Every wall, floor, or containment-box penetration is a place the system can be compromised if not detailed correctly.
Valve / access boxes
Valves are where a double-contained run is most often improvised — the box has to carry the same containment discipline as the pipe.
Discrete-Point vs. Continuous Cable — Real Products, Real Tradeoffs
Discrete-Point Detection
Strength: Straightforward, lower cost.
Weakness: Leakage has to physically reach the sensor location.
Icon LD Sensor (adjustable sensitivity, NEMA 4X) and LDS-YN electrostatic sensor — explicitly engineered for the interstitial area between double-wall tanks, retention dikes, and secondary containment sumps.
Continuous Sensing Cable
Strength: Earlier detection over long runs, can localize the leak.
Weakness: Higher complexity — installation and maintenance matter.
Icon LDC CablPro (self-wicking, non-conductive PE, explicitly marketed for dual-containment or insulated piping) paired with LeakPoint — 492 ft (150m) sensing range over RS485 Modbus, reporting where along the cable the leak occurred, not just a binary alarm. Asahi's own PAL-AT cable-based system does the same job on the Duo-Pro line.
The right answer depends on consequence and geometry — not a default choice.
What LibertyCES Specifies for Double-Contained Chemical Piping
Duo-Pro Double Containment Piping
PP, PVDF, or ECTFE — sizes 1x3 through 16x20, 150 psi plus drainage ratings. Outer pipe designed to meet the EPA standard of at least 30 days of containment. Leak-detection cable installable on 2x6 and larger via Asahi's own PAL-AT system.
480 Dual Containment Tubing
Tube-in-tube design: 100% virgin Daikin AP-231SH UHP PFA inner tube (SEMI F-57 and C-90 approved) inside a clear FEP outer tube, so a leak in the inner tube is visually detectable without disassembly.
Full specs: Asahi/America Manufacturer Hub · Pexco / Altaflo Manufacturer Hub.
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30+ years specifying industrial chemical and fluid-handling equipment. Containment runs on the same Zero-Guesswork Specification Framework as every other system — what happens if this pipe leaks, and how is it detected, are questions with a documented answer before installation, not after.
Frequently Asked Questions
Is putting one pipe inside another enough for double containment?
No — that's the beginning of the engineering, not the finished solution. The annular space has to be treated as its own functioning system: supports, expansion allowance, drainability, leak detection, inspection access, low points, termination points, penetration design, and valve/access boxes all have to be explicitly engineered.
What happens without leak detection on a double-contained line?
The carrier pipe can fail and go unnoticed until the secondary containment itself becomes compromised. Asahi specifically emphasizes leak detection in properly designed double-contained piping for exactly this reason — containment without detection just delays discovery of the failure.
Does the secondary containment pipe have to be the same material as the carrier pipe?
No — the real question is whether the secondary system can safely contain the actual chemical under the expected exposure conditions until shutdown, isolation, and repair occur. That has to be an explicit engineering decision, not an assumption that matching materials automatically means matching performance.
Discrete-point or continuous cable — which leak detection method should I use?
It depends on consequence and geometry. Discrete-point sensors are simpler and lower cost but only catch a leak once it physically reaches the sensor. Continuous cable detects earlier over long runs and can localize where along the run the leak occurred — Icon's LDC CablPro paired with LeakPoint reports location over a 492 ft (150m) range via RS485 Modbus.
Tank-Level Double-Wall Containment
This guide covers piping. For double-wall storage tank containment, see Double-Wall Secondary Containment Tanks.