PEX-A
Premium PEX-A Pipe
Conversions Tech® PEX-A pipe is the go-to solution for leak-free potable-water plumbing, radiant floor heating, and hydronic loops. Made with Engel-method cross-linked polyethylene, it bends tight, springs back from kinks, and cold-expands to lock on ASTM F1960 fittings—no clamps, no leaks, no callbacks.
- 200 °F & 200 psi performance rating
- NSF 14/61, ASTM F1960 & F877 compliant
- Red, blue, white & purple coils ⅜″–1″
Upgrade to Conversions Tech® PEX-A—faster installs, fewer fittings, longer life.
Conversions Tech® Deep-Dive FAQ: PEX-A & PEX-B Pipe
Last reviewed — June 2025; code references current to the 2024 IRC/UPC editions.
1. What exactly is the difference between PEX-A and PEX-B?
| Property | PEX-A (Engel / Peroxide) | PEX-B (Silane / Moisture-cure) |
|---|---|---|
| Cross-link density | ≥ 70 % (highest) | 65 – 70 % |
| Flexibility / bend radius | Very tight (≈ 6 × OD) | Moderate (≈ 8 × OD) |
| Kink-recovery | Full (heat-gun fix) | Limited — may crack |
| Cold-expansion use | Ideal (ASTM F1960) | Generally not recommended |
| Chlorine/oxidant resistance† | Class A (good) | Class B–C (better) |
| Cost per coil | 5 – 10 % higher | Lower |
†Rating varies by manufacturer; confirm ASTM F2023 classification printed on the pipe.
2. Pros and cons in real-world plumbing
| Aspect | PEX-A | PEX-B |
|---|---|---|
| Pros |
• Ultra-flexible—sweeps around studs without elbows • Cold-expands for 360° compression seal (no crimp rings) • Best for manifold “home-run” layouts |
• Lower material cost • Stiffer wall resists sag on long trunk lines • Slightly higher chlorine tolerance in aggressive water |
| Cons |
• Higher price per foot • Softer wall can scuff during pull-through |
• Needs metal crimp/clamp ring (adds head-loss) • Kinks must be cut out (no full recovery) • Not compatible with ASTM F1960 tool sets |
3. Which fitting families match each pipe?
| Fitting Standard | Pipe Type | Connection Method | Material |
|---|---|---|---|
| ASTM F1960 | PEX-A (occasionally B) | Cold-expansion + sleeve | No-lead brass / PPSU |
| ASTM F1807 / F2159 | PEX-A & PEX-B | Copper crimp or SS clamp | Brass (F1807) / Poly (F2159) |
| ASTM F2080 | Any SDR-9 PEX | Metal compression sleeve | DZR brass |
| Push-to-Connect | All PEX | O-ring + grab ring | Brass / Polymer |
Takeaway: PEX-A can use any SDR-9 fitting, but only it maximizes the flow benefits of ASTM F1960 cold-expansion.
4. Where is PEX used—and where should it not be used?
| Application | Suitability | Notes |
|---|---|---|
| Hot & cold potable water | ✔️ | NSF 61 listing required; derate above 140 °F. |
| Radiant floor / hydronic | ✔️ | Use oxygen-barrier PEX in closed loops. |
| Snow-melt / geothermal | ✔️ | Handles aggressive cycling; bury below frost. |
| Fire-sprinkler (NFPA 13D) | ⚠️ | Pipe & fittings must carry fire listing. |
| Compressed air | ❌ | Embrittlement risk; use HDPE or metallic tube. |
| Fuel oils / gasoline | ❌ | Hydrocarbon permeation & swelling. |
| 185–200 °F recirc lines | ⚠️ | Select PEX with extended 200 °F rating or switch to PP-R/CPVC. |
| Outdoor UV exposure | ❌ long-term | Limit to < 60 days or sleeve/insulate. |
5. How do pressure & temperature ratings compare?
All SDR-9 PEX (A or B) carries identical baseline ratings under ASTM F876:
- 100 psi @ 180 °F
- 160 psi @ 73 °F
- 200 psi @ 73 °F (intermittent < 100 °F)
*Always apply manufacturer derating charts for continuous recirculation above 140 °F.
6. Oxygen-barrier vs. non-barrier PEX
- Barrier PEX with EVOH/aluminum layer blocks O2 diffusion—critical in closed-loop boiler circuits.
- Non-barrier PEX is ideal for potable water where dissolved oxygen already exists.
7. Pitfalls when mixing PEX systems
Interchange only when standards match:
- Do not pair an ASTM F1960 sleeve with an F1807 brass barb—diameters differ.
- Copper crimp rings (F1807) and SS clamps (F2098) aren’t interchangeable.
- Manifold ports must match pipe OD; ⅝″ PEX uses a unique ¾″ OD.
8. How does freeze resistance really work?
PEX can balloon ~10 % without rupture. Once thawed, PEX-A recovers fully; fittings, however, do not flex—keep joints out of unconditioned spaces or insulate adequately.
9. What codes & markings should I look for?
PEX-A SDR-9 1/2" ASTM F876/F877 NSF-14/61 CL-TD P/N #### Date ####
- NSF 61 — drinking-water contact
- NSF 14 — plastic pipe system
- CSA B137.5 — Canadian listing
10. Bottom-line decision matrix
| If you value… | Choose this |
|---|---|
| Fastest installs, tightest bends | PEX-A + ASTM F1960 cold-expansion |
| Lowest up-front cost | PEX-B + copper crimp rings |
| High-chlorine municipal water | PEX-B Class B/C or PEX-A with proven Class A rating |
| Ease of repair with universal couplings | Any PEX + push-to-connect fittings |
11. Can PEX integrate with copper or CPVC?
Yes—use transition fittings:
- ASTM F1960 / F1807 PEX barb × sweat or press adapters
- Brass stub-outs behind drop-ear elbows for valves
- Dielectric unions when tying into galvanized steel
12. Future-proofing tips for installers
- Color-code runs (red = hot, blue = cold, purple = reclaimed, white = universal).
- Label all manifold ports before closing walls.
- Document tool brand & ring size for maintenance crews.
Need niche guidance? Contact Conversions Tech® Engineering Support
Our team of licensed plumbers and mechanical engineers will walk you through glycol mix limits, fire-rated assemblies, tool calibration, and more.
