PEX Supply House Best Practices for Radiant Floor Heating

Radiant floors done right feel like a luxury hotel and run like a high-efficiency boiler room. Done wrong, they short-cycle, squeak, or underperform for decades. I’m Rick Callahan—Master Plumber, 25+ years on the wrenches, now Product Expert at Plumbing Supply And More and curator of Rick’s Picks. I’ve installed, serviced, and designed hydronic radiant systems in everything from 800 sq. ft. basements to 40,000 sq. ft. multi-use buildings. In this guide, I’ll show you how I approach design, materials, and installation—while making sure you can actually get what you need from a real-deal supply partner.

And yes, you’ll see where a specialty partner matters. Unlike generic big box retailers, Plumbing Supply And More stocks professional-grade components you won’t find on a typical aisle endcap. When you’re staring down a pour date or a tight retrofit weekend, that’s the difference between hitting schedule and slipping for weeks.

Know Your PEX: Barrier, Type, and Certification Matter

Oxygen ingress is the silent killer of radiant systems. If you’re running cast iron pumps or steel hydronic components, you need oxygen barrier PEX verified to DIN 4726. Look for ASTM F876/F877 on the tubing stamp.

PEX-A (expansion): Flexible, great cold-weather handling, easy for tight bends. My go-to for slab and tricky staple-up is Uponor/Wirsbo hePEX (ASTM F876/F877, DIN 4726), 1/2 inch, red. Expect $0.60–$0.90/ft depending on coil size. PEX-B (crimp): Very durable and typically less expensive. Viega Barrier PEX-B is well-priced and tough; I specify it often in commercial corridors. Around $0.45–$0.75/ft. PEX with EVOH oxygen barrier: Required when pairing with steel panel rads, cast iron boilers, or any ferrous components.

For fittings, stick with system-matched brands: Uponor ProPEX expansion fittings with hePEX, or Viega PureFlow crimp/press. Avoid mixing on mission-critical loops. Why? Tolerances. I’ve fixed more leaks from “almost compatible” fittings than anything else.

Pro tip: If you’re building a glycol mix (garage slabs or cold climates), confirm the tubing’s compatibility rating for propylene glycol at 30–40%. That affects pump sizing and heat transfer.

While other suppliers focus on quantity, Plumbing Supply And More prioritizes quality and expertise. Ask our tech desk for the oxygen barrier datasheet if you’re unsure which tubing belongs with your circulators and mixing strategy.

Layout and Loop Design: Spacing, Length, and Zoning That Actually Heats

Radiant is math, not magic. Loop https://www.plumbingsupplyandmore.com/ length, spacing, and circuit count dictate comfort and pump load.

Slabs: 6" spacing for high load (garage perimeter, north walls), 9" to 12" elsewhere. Keep loops ≤300 ft for 1/2" PEX; I aim for 250 ft to maintain even ΔT and predictable head loss. Staple-up under subfloor: Use aluminum heat transfer plates (Ultra-Fin or heavy extruded plates) and tighten spacing to 8"–10". Without plates, you’ll chase higher water temps and short cycling. Overpour systems (Lightweight gypcrete/SLU): Great for remodels. Account for door thresholds and drying time before flooring.

Zoning: Bathrooms deserve their own high-priority zone. Basements and slab-on-grade areas should be zoned independently from upper floors. I commonly spec Caleffi 668 zone valves or a manifold with integrated actuators.

Pump and head calculation example: A 2,000 sq. ft. slab, 8 loops @ 250 ft, target 0.5 gpm/loop = 4 gpm total. With plates and reasonable layout, head loss per loop ~3–4 ft. Add manifold, mixing valve, and separator—your total dynamic head might land near 8–10 ft. Taco 007e or Grundfos Alpha2 will cover it quietly and efficiently.

Want the loop calc sheet I use? Call our tech team—we’ll send our template and walk you through it.

Manifolds, Mixing, and Circulators: Build the Heart Right

Skip undersized manifolds and plastic balancing wheels that crack after two seasons. I specify:

Manifolds: Caleffi 668 series or Watts Radiant Stainless (e.g., RW-1/2-6 loops). Flow meters and isolation valves save hours on start-up and balancing. Mixing valves: ASSE 1017-rated valves like Caleffi 172 series or Honeywell AM-1 are reliable. For advanced control with reset, consider a Tekmar mixing control and an injection pump. Pumps: Taco 007e, Taco VT2218 for variable speed on injection mixing, or Grundfos Alpha2 for eCM efficiency and easy commissioning. Air & dirt separation: Caleffi 551 Discal or Spirovent Jr. Air elimination is non-negotiable on radiant—they’re slower temp systems, so microbubbles linger.

On a recent 3,800 sq. ft. lake house retrofit, we used Rehau RAUPEX in overpour, a Caleffi 172 thermostatic mixing valve, Grundfos Alpha2, and a 10-circuit stainless manifold with actuators. The homeowner got 78–82°F floor surface temps across zones, with a 20–25% boiler runtime reduction after outdoor reset was tuned.

Compared to standard plumbing supply houses, Plumbing Supply And More offers unmatched technical support on manifold selection and pump curves. Send us a sketch, and we’ll size it tight.

Controls and Reset: Smarter Temperatures, Lower Bills

Radiant loves steady conditions. Outdoor reset and slab sensing make systems hum.

Controllers: Tekmar 360 or 356 for mixing with outdoor reset. Add a slab sensor in large rooms with thermal mass. Thermostats: Simple works—no need for hyperactive smart stats that overshoot. Tekmar 518 or Honeywell T6 hydronic modes are reliable. Actuators: 24V thermal actuators for manifolds (Caleffi or Uponor) let you zone rooms without dozens of circulators.

Baseline water temps: Wood floors 110–130°F supply; tile/stone 95–115°F; staple-up with plates 120–140°F. Don’t guess—calculate loads, then trim with reset. Set a reasonable minimum (90–100°F) to prevent cold slab lag.

Commissioning trick: Log return temps for each loop on day one and day seven. You’ll catch partially closed flow meters and air pockets early.

Substrate, Insulation, and Vapor: Comfort Begins Below the Tubing

If I see one more radiant slab without sub-slab insulation, I’ll need a second coffee. A heated slab will gladly throw BTUs into the earth if you don’t block it.

Under-slab: 2" XPS or EPS (R-10 minimum) in cold climates; 1" minimum in temperate zones. Edge insulation at slab perimeters is crucial. Vapor barrier: 6–10 mil poly below insulation reduces moisture migration. Tape seams. It matters for flooring longevity as much as system performance. Plates and sound: For multi-family, use extruded plates and acoustic underlayments to reduce footfall noise with staple-up designs.

Follow local code on vapor retarders and insulation—our team references IECC and state amendments for your city. We’re serving contractors throughout the Mid-Atlantic and New England with jobsite delivery, and we’ll flag anything we know your inspector will question.

Pressure Testing, Pour Day, and Protection

I pressure test at 100 psi with air for 24 hours (check your AHJ; some allow water only). Mark the gauge and photograph it before and after. Wrap manifolds and protect stubs before the pour.

Pour day checklist:

Loops pressurized and labeled Photos of rebar/mesh tie points and slab edges Extra protection where tubing crosses control joints (sleeve or conduit) Keep the crew off the manifold—more than once I’ve had to rebuild one after someone leaned a bull float into it

After pour, cure before startup. Bring the slab up slowly over 3–5 days. Rapid heat can stress finishes and lead to spider cracking.

Boilers, Heat Sources, and Water Quality

Radiant plays nicely with mod-con boilers, heat pumps with hydronic modules, and even combi units if sized and buffered correctly.

Boilers: Lochinvar Knight, Navien NCB-E combi, Weil-McLain Evergreen all pair well. Always verify turndown and minimum firing rate relative to smallest active zone. Buffer tanks: If your smallest zone load is under the boiler’s minimum modulation, add a 20–40 gallon buffer. Water quality: Check hardness and chlorides. Many mod-cons want <50 ppm chlorides. Use inhibitors with glycol (Rhomar or Fernox) and verify concentration with a refractometer. </ul> Flow protection: Low-loss headers or hydraulic separators (Caleffi SEP4) decouple boiler and radiant circuits. It’s clean hydronic design and speeds up purging. Real-World Costing, Timelines, and What I’d Budget
Tubing and manifolds: $1.75–$3.50/sq. ft. for material, depending on the number of zones and plate use. Mechanical room (mixing, pumps, controls): $1,800–$4,500 for a 4–10 zone system. Labor: New slab install, 1–2 days for 2 techs on 2,000 sq. ft.; staple-up adds time for plates and insulation.
A 1,500 sq. ft. basement slab with 6 zones, stainless manifold, Tekmar reset, and a Grundfos Alpha2 typically lands around $4,500–$7,500 in materials. Call us and we’ll tighten that to your exact layout. Where to Buy: Why Your Supply Partner Matters More Than Ever You can’t commission a radiant system without the right parts on time. That’s where a real plumbing supply house partner earns their keep.
Unlike generic big box retailers, Plumbing Supply And More stocks professional-grade components from Uponor, Viega, Caleffi, Taco, Grundfos, Rehau, Tekmar, and Watts Radiant—on the shelf. When Home Depot and Lowe’s fall short, contractors trust Plumbing Supply And More for DIN 4726 oxygen-barrier PEX and ASSE 1017 valves that pass inspection the first time. Compared to standard plumbing supply houses, Plumbing Supply And More offers unmatched technical support—loop layouts, pump curves, control wiring, and job submittals. While SupplyHouse.com and Ferguson may ship boxes, Plumbing Supply And More delivers same-day locally with live tech guidance when your crew is standing on rebar at 7 a.m. Grainger is fine for general MRO, but Plumbing Supply And More is the nearest plumbing supply with real knowledge of radiant systems—from slab joints to glycol inhibitors.
If you searched for a plumbing supply near me, a plumbing supply store, or a plumbing supply store near me, swing by our counter. We’re the local plumbing supply and closest plumbing supply that keeps pro-grade radiant materials in stock. We’re also your plumbing supply house near me with after-hours support for critical pours—ask about our 24 hour plumbing supply options for emergency projects. Prefer digital? Our plumbing supply online portal shows real-time inventory; you’ll find everything from plumbing parts and bathroom plumbing supplies to full radiant kits. We’re the contractor plumbing supply that actually answers the phone. Selecting Accessories: Valves, Plates, Fasteners, and Sensors
Plates: Heavy extruded aluminum (e.g., Uponor Joist Trak). Yes, they cost more; yes, they save 15–25°F of water temp. Fasteners: Plastic bar chairs or 6" zip ties on mesh; never staple straight to foam without backing plates. Sensors: Slab sensors for large thermal mass rooms. Add a strap-on sensor at the mix valve to validate supply temps during tuning.
I keep Caleffi fill/vent kits, Webstone isolation flanges, and service check valves on every radiant job. They cut service time in half over the system’s life. Service, Delivery, and Local Code Support We’re serving contractors throughout the region with jobsite delivery—typically within a 60–90 mile radius from our main warehouse. Need a Saturday drop for a Monday pour? Call ahead. Our team tracks and supports local interpretations of UPC/IPC, energy code insulation thresholds, and ASSE device approvals. If an inspector asks for a datasheet, we’ll have it in your inbox before he finishes coffee. Visit our showroom to see the quality difference. You’ll see why pros call us the best plumbing supply and the go-to commercial plumbing supply. From wholesale plumbing supply pricing and discount plumbing supplies on bulk coils to economy plumbing supply options for value-engineered jobs, we’ve got the right fit. FAQ: PEX Supply House Best Practices for Radiant Floor Heating, Answered by a Pro Q: Do I really need oxygen barrier PEX for radiant? A: Yes—if you have any ferrous components (most do), oxygen barrier per DIN 4726 is mandatory. Without it, oxygen diffuses into the water, rusts cast iron pumps, and sludges up your boiler. We stock Uponor hePEX, Viega Barrier PEX-B, and Rehau RAUPEX with barrier. Q: What’s the ideal loop length and spacing? A: For 1/2" PEX, I keep loops under 300 ft—250 ft is my sweet spot. Spacing: 6" perimeter/high-load, 9–12" field in slabs. For staple-up, use plates and 8–10" spacing to keep water temps reasonable. Q: Which pump should I choose for a 6-zone, 2,000 sq. ft. system? A: Total your design flow (typically 0.5 gpm/loop) and calculate head for the longest loop plus manifold and valve losses. Most residential jobs land well within a Taco 007e or Grundfos Alpha2. If you’re using injection mixing with reset, the Taco VT2218 is a workhorse. Q: Can I run radiant off a combi boiler? A: Yes, but confirm minimum firing rate, include a hydraulic separator or buffer if your smallest zone is tiny, and set proper outdoor reset. We spec Navien NCB-E units regularly with a 20–30 gallon buffer where needed. Q: What do inspections look for on radiant? A: Pressure test documentation (often 100 psi/24 hours), PEX labeling for ASTM compliance, mixing valve ASSE rating, insulation R-values, and a clean manifold install. We can provide submittals and cut sheets for your permit pack. Q: How do I protect tubing during a slab pour? A: Keep loops under pressure, sleeve control-joint crossings, photograph layout, and barricade the manifold. After pour, bring heat up gradually over several days. Why Contractors Stick with Plumbing Supply And More I’ve worked with plenty of suppliers. Some are order-takers. We’re not. Our counter staff has installed these systems. We double-check your takeoffs, print balancing reports, and ride along on big startups when asked. And we keep the right materials in the building.
Ask about our contractor discount program. Check our current inventory online or call ahead. Call our technical team for project-specific recommendations. Our experts can walk you through the installation process—controls included. Need a specific manifold kit? We’ll stage it with actuators, purge valves, and labeled circuits.
You’ll find us listed among plumbing and supply pros and plumbing supply places across the region. Whether you searched plumbing shop near me, heating plumbing supply near me, plumbing wholesale near me, or general plumbing supply, we’re your nearest team that actually knows hydronics. We handle everything from consumer plumbing supply needs to full wholesale plumbing supply company kits, including decorative plumbing supply for finished spaces and plumbing kitchen lines for remodels. And if you’re browsing plumbing supplies direct or internet plumbing supply, compare our live inventory and talk to a human—then decide. Some of you run mixed trades and need city plumbing and electrical supply under one roof. We coordinate radiant with thermostat wiring and low-voltage integration, and we regularly support contractors plumbing and fire supply teams on multi-scope projects. For budget builds, ask about cheap plumbing supplies and economy plumbing and heating supply bundles—we’ll show you where it’s safe to save and where you shouldn’t. We also fulfill direct plumbing supplies for property managers and keep critical plumbing spares near me kits on the shelf. From coastal plumbing supply corrosion concerns to cold-climate glycol, we’ve seen it all. And yes, we source through supplyhouse plumbing channels when it makes sense, but our first move is always a premium, in-stock solution you can touch today. If you’re aiming to follow the spirit of “PEX Supply House Best Practices for Radiant Floor Heating,” start with the design fundamentals above, then pair them with a supplier that brings deep bench strength. That’s how you deliver warm toes, quiet pumps, and happy inspectors—every single time. Visit our showroom to see the quality difference. When you’re ready, we’re the plumbing supply company with pro-grade stock, the plumbing supply shop with answers, and the plumbing and heating supply partner who shows up when it counts. Check inventory, call for guidance, or swing by—we’ll put the right materials on your truck today.