Plumbing Tools

Plumbing Calculator

Calculate pipe lengths, fixture costs, and plumbing material estimates. Plan your plumbing rough-in and finish work accurately.

Plumbing Calculations

Material Estimates

Total Fixtures 0
Pipe Length 0 feet
Water Supply Line 0 ft
Drain/Waste Line 0 ft
Fittings Needed 0
Material Cost $0
Labor Cost $0

Fixture Unit Counts

Toilet: 3 units

Bathtub/Shower: 2 units

Lavatory: 1 unit

Kitchen Sink: 2 units

Dishwasher: 2 units

Pipe Size Guidelines

  • 1/2" for sinks and lavatories
  • 3/4" for toilets and showers
  • 1" for main drains
  • 1-1/2" for main water supply

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Plumbing Calculator for Construction Projects

Accurate plumbing calculations are essential for proper water flow, drainage, and code compliance. Our free plumbing calculator helps contractors estimate pipe lengths, fixture costs, and material requirements for residential and commercial plumbing systems.

Understanding Fixture Units

Plumbing fixtures are measured in "fixture units" to determine pipe sizing and drainage capacity:

  • Toilet: 3 fixture units (water closet)
  • Bathtub/Shower: 2 fixture units
  • Lavatory/Sink: 1 fixture unit
  • Kitchen Sink: 2 fixture units
  • Dishwasher: 2 fixture units
  • Washing Machine: 2 fixture units

Pipe Material Selection

Choose the right pipe material for your application:

  • Copper: Durable, corrosion resistant, expensive
  • PVC: Inexpensive, easy to install, for drain/waste/vent
  • PEX: Flexible, freeze resistant, for water supply
  • Galvanized Steel: Strong, inexpensive, prone to corrosion

Plumbing Rough-In Planning

Proper rough-in measurements prevent costly mistakes:

  • Measure center-to-center distances between fixtures
  • Account for pipe slope (1/4" per foot for drainage)
  • Include access space for repairs and maintenance
  • Follow local plumbing codes for minimum distances
  • Plan for future fixture additions

Drainage System Design

Drainage systems must handle peak flow while maintaining proper slope:

  • Minimum slope: 1/4" per foot for horizontal drains
  • Cleanouts required every 100 feet and at direction changes
  • Vent pipes extend through roof at least 6" above roof surface
  • Traps required for each fixture to prevent sewer gas entry
  • Proper venting prevents siphoning and ensures drainage

Plumbing FAQ

How much pipe do I need for plumbing?

Measure the distance between fixtures and add 10-15% for fittings and waste. Use 1/2 inch pipe for sinks, 3/4 inch for toilets and showers, 1 inch for main drains. Always include extra pipe for fittings - each elbow and tee requires additional length.

How many plumbing fixtures can I have?

Plumbing fixture counts are regulated by local building codes based on building occupancy. Residential bathrooms typically have 1.5-2 fixture units. Commercial buildings require more fixtures based on number of occupants and building use. Always check local codes.

What's the difference between supply and drain pipe sizing?

Supply pipes are sized for pressure and flow rate, while drain pipes are sized for gravity flow and fixture unit capacity. Supply pipes get smaller as they branch out (1-1/2" main, 3/4" branches, 1/2" fixtures). Drain pipes get larger as they combine (1/2" fixture, 1-1/2" main drain).

Do I need to vent all plumbing fixtures?

Yes, proper venting is required for all plumbing fixtures to prevent siphoning, ensure proper drainage, and allow sewer gases to escape. Wet venting combines drain and vent functions. Individual vents extend through the roof. Always follow local plumbing codes for venting requirements.

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