BuildMeter guide · Water & Mechanical
Radiant-Floor PEX Loop Planning Guide
Lay out tube spacing and loop limits before ordering tubing and manifolds. Includes measurement workflow, a worked example, decision table, ordering checkpoints, common failures and professional boundaries.
Direct answer
What to know first
Lay out tube spacing and loop limits before ordering tubing and manifolds.
Open PEX Tubing Length CalculatorDefine the project boundary first
Lay out tube spacing and loop limits before ordering tubing and manifolds. Record the design condition, measured scope, operating schedule and product assumptions before comparing quantities or costs. Keep code-controlled values separate from editable planning assumptions.
Worked example
A 600 ft² heated area laid at 12 in spacing has a geometric tubing baseline near 600 linear ft before leaders and layout effects. If the selected design limits each loop to 250 ft, that baseline requires at least three loops; actual loop lengths should be balanced and include supply/return leaders to the manifold.
Planning decision table
| Checkpoint | Verify | Record |
|---|---|---|
| Demand | Field measurements and design condition | Unrounded requirement |
| Performance | Rated capacity at actual conditions | Efficiency or usable yield |
| Distribution | Route, support, controls and losses | Adjustment factors |
| Purchase/operation | Package size, equipment count or runtime | Rounded final quantity |
Measurement and calculation workflow
- Sketch the connected system and divide it into independently measurable sections.
- Use one unit system and label every design-controlled input.
- Calculate the raw demand before efficiency, diversity, allowance or tariff adjustments.
- Apply each adjustment once and document why it is appropriate.
- Round only the final purchasing or equipment-count result and reconcile the surplus.
Ordering and coordination
Confirm tubing diameter, manufacturer loop-length limits, spacing, manifold location and floor assembly before ordering. Keep total tubing length and number of hydraulic loops as separate design outputs.
Common project failures
- Using nominal ratings without checking the actual design condition.
- Mixing peak demand with daily or annual energy.
- Hiding multiple allowances inside one input.
- Ignoring distribution losses, cycling or control strategy.
- Ordering before field dimensions and connection requirements are verified.
How to interpret calculator results
Use the calculator to test tubing length and loop count, not to infer water temperature, flow or heating capacity automatically. Those depend on room loads and floor construction.
Technical references and limits
This guide supports radiant-tubing layout planning. Heat-loss design, water temperature, flow balancing, controls and floor-temperature limits require a qualified hydronic design.