Radiant Floor Pipe for 80 m2 - How Much PEX Tubing?

Six pipe systems in one tool

Cold water, hot water, drain lines, radiant floor loops, radiator circuits and gas - each system uses different pipe materials, diameters and fitting types. This calculator covers all six. Select your system, enter the number of fixtures (or heated floor area for radiant), average run length and number of floors. The result: total pipe footage with surplus, fitting count (elbows, tees, couplings), diameter recommendations and an optional material cost breakdown.

How to use the calculator - step by step

Choose system type - cold water, hot water, drain/waste, radiant floor, radiator heating or gas. Each type sets the correct pipe material and diameter automatically.
Enter fixture count - total number of connection points (faucets, drains, radiators). A typical 3-bedroom house has 8-12 fixtures. For radiant floor heating, this field is replaced by heated floor area.
Enter average run length - the typical distance from the manifold or main riser to each fixture, in meters. Single-story: 4-8 m (13-26 ft). Two-story: 6-12 m (20-40 ft).
Select number of floors - each additional floor adds vertical risers and extra fittings.
For radiant floor - enter heated area in m2 and loop spacing (4, 6 or 8 in). The calculator computes loop count and total tubing length.
Read the results - total pipe in meters and feet, fitting breakdown, diameter recommendation, and optional cost estimate.

Pipe material and diameter atlas

Each system type maps to specific pipe materials and diameters. Using the wrong material causes code violations, leaks or warranty issues.

System	Material	Main line	Branches	Key rule
Cold water	PE, PP, PEX	1 in	3/4 in	Blue stripe or blue pipe
Hot water	PP stabi, PEX, Cu	1 in	3/4 in	Red stripe; stabilized only
Drain/waste	PVC, PP	4 in	2 in	1/4 in/ft slope minimum
Radiant floor	PEX-a, PERT	5/8 in (16 mm)		Max 330 ft per loop
Radiator	PP, PEX, Cu	1 in	1/2-3/4 in	Two-pipe system standard
Gas	PE, black steel	1 in	3/4 in	Licensed installer only

Practical examples

Example 1: Cold water, 8 fixtures, 2-story house - avg run 6 m, 15% surplus
Result: 114 m (374 ft) of PE/PP pipe, 24 elbows, 7 tees, 4 couplings

Example 2: Drain/waste, 10 fixtures, 2-story - avg run 5 m, 15% surplus
Result: 69 m (226 ft) of PVC pipe, 31 elbows, 8 tees, 5 couplings, 4 cleanouts

Example 3: Radiant floor, 80 m2, 6 in spacing - 15% surplus
Result: 637 m (2,090 ft) of PEX, 6 loops, 24 elbows, 12 couplings, 1 manifold

Example 4: Radiator heating, 6 radiators, single-story - avg run 5 m, 10% surplus
Result: 66 m (217 ft) of PP/PEX, 15 elbows, 5 tees, 3 couplings

Example 5: Gas, 3 appliances, single-story - avg run 8 m, 15% surplus
Result: 56 m (184 ft) of PE/steel, 8 elbows, 3 tees + licensed installer required

FAQ - Frequently asked questions

What is the maximum loop length for radiant floor heating?

For 5/8 in (16 mm) PEX, the maximum loop length is 330 ft (100 m). For 3/4 in (20 mm) PEX, it extends to 400 ft (120 m). Exceeding these limits causes excessive pressure drop and uneven heating. The calculator automatically splits large areas into multiple loops of the correct length.

PEX vs copper vs CPVC - which is best for water supply?

PEX is the most popular choice: flexible, freeze-resistant, cheap ($0.50-1.50/ft), easy to install with crimp or push fittings. Copper is durable and code-approved everywhere, but costs 3-5x more and requires soldering. CPVC sits in between - rigid like copper, glued joints, cheaper than copper but not as flexible as PEX. For most residential projects, PEX is the best value.

What slope do drain pipes need?

The minimum slope for horizontal drain pipes is 1/4 in per foot (2%) for pipes 3 in and smaller, and 1/8 in per foot (1%) for 4 in pipes per IPC/UPC code. Too little slope causes standing water and clogs. Too much slope (over 1/2 in/ft) causes water to run ahead of solids, also causing clogs.

How many fixtures can one 3/4 in supply line serve?

A single 3/4 in supply line can typically serve 6-8 fixtures at adequate pressure. Beyond 8 fixtures or when the incoming pressure is below 40 psi, upsize the main to 1 in. The exact limit depends on pipe length, number of elbows (each elbow adds ~2 ft equivalent length), and water pressure at the meter.

Do I need a permit for plumbing work?

In most US jurisdictions, any work beyond replacing a faucet or toilet requires a plumbing permit. New supply lines, drain rerouting, water heater installation and gas piping always require permits and inspections. Some states allow homeowners to pull their own permits for their primary residence. Gas work universally requires a licensed gas fitter regardless of permit rules.

How much surplus pipe should I order?

Order 10% extra for simple, straight runs (basement utility room). 15% is standard for typical residential jobs with some bends and wall penetrations. 20% for complex layouts with many turns, floor penetrations and manifold connections. PEX comes in 100 ft or 300 ft rolls - round up to the nearest full roll to avoid splicing mid-run.

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Radiant floor tubing for 80 m2 - total length and loops

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