Plumbing Basics Cheat Sheet

Pipe sizes, materials, fittings, and drainage requirements for residential plumbing. Great foundation for DIY plumbing repairs and installations.

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Pipe Sizes & Applications
SizeMaterialCommon Uses
1/2"PEX, CopperSupply lines to fixtures
3/4"PEX, CopperMain water lines, multiple fixtures
1"PEX, CopperService entrance, manifolds
1-1/4"PVC, ABSSink drains
1-1/2"PVC, ABSBathtub, shower drains
2"PVC, ABSWashing machine, branch drains
3"PVC, ABS, Cast IronToilet drains, main stacks
4"PVC, ABS, Cast IronMain sewer line, stacks
Pipe Materials

PEX (Cross-linked Polyethylene)

  • Flexible, easy to install
  • Freeze-resistant
  • Not for outdoor use (UV sensitive)
  • Requires special tools and fittings

Copper

  • Types: M (thin), L (standard), K (thick)
  • Durable, heat-resistant
  • Requires soldering or compression fittings
  • Can corrode in acidic water

PVC (Polyvinyl Chloride)

  • White pipe for cold water drains
  • Not for hot water
  • Glued with PVC cement
  • Inexpensive, easy to work with

ABS (Acrylonitrile Butadiene Styrene)

  • Black pipe for drains
  • Similar to PVC, more flexible
  • One-step cement (no primer)
  • Not allowed in all areas
Drainage & Venting

DWV Slope Requirements

  • Minimum slope: 1/4" per foot
  • Maximum slope: 3" per foot (to prevent siphoning)
  • Check slope with level before securing

Vent Requirements

  • Every fixture needs a vent
  • Vent must slope upward from drain
  • Minimum vent size: 1-1/4" (often 2")
  • Vents must extend through roof or tie to existing vent

Trap Requirements

  • P-trap for sinks, showers, tubs
  • Toilets have built-in trap
  • Trap arm: max 2x pipe diameter from trap to vent
  • Keep traps accessible for cleaning
Water Pressure & Flow

Normal Pressure: 40-60 PSI

Maximum: 80 PSI (PRV required above)

Minimum: 30 PSI (fixtures may not work properly)

Flow Rates:

  • Shower: 2.5 GPM
  • Faucet: 2.2 GPM
  • Toilet: 1.6 GPF (gallons per flush)
  • Dishwasher: 1-2 GPM
  • Washing Machine: 2-3 GPM
Common Fittings

90° Elbow

Right angle turn

45° Elbow

Gentler angle turn

Coupling

Join two straight pipes

Tee

Three-way connection

Wye

45° branch connection

Reducer

Change pipe size

Cap

Close end of pipe

Union

Removable connection

Soldering Copper Pipe
  1. Cut pipe square with tube cutter
  2. Deburr inside and outside of pipe
  3. Clean pipe and fitting with emery cloth or wire brush
  4. Apply flux to pipe end and inside fitting
  5. Assemble joint and wipe excess flux
  6. Heat joint evenly with torch until flux bubbles
  7. Touch solder to joint (not torch flame)
  8. Solder should flow into joint by capillary action
  9. Remove heat when solder ring appears
  10. Let cool naturally, wipe excess solder
Emergency Shutoffs
  • Main Shutoff: Usually near water meter or where service enters
  • Fixture Shutoffs: Under sinks and toilets (angle stops)
  • Water Heater: Cold water inlet valve at top of tank
  • Outdoor Hose Bibs: Interior shutoff valve to prevent freezing
  • Know locations before emergency occurs
  • Test valves annually to ensure they work

Additional Information

About This Plumbing Basics Guide

This plumbing basics cheat sheet provides essential reference information for DIY homeowners tackling common plumbing projects. From understanding pipe sizes and materials to proper drain slope requirements, this guide covers the fundamental knowledge you need for successful plumbing repairs and installations.

Whether you're replacing a faucet, fixing a leaky pipe, installing a new toilet, or planning a bathroom renovation, understanding plumbing basics helps you work more efficiently and avoid costly mistakes. This reference includes pipe sizing for supply and drain lines, material selection guidance, soldering techniques, and critical venting requirements that ensure your plumbing system functions properly.

Plumbing work requires attention to detail and adherence to local codes. While many homeowners can successfully handle basic repairs, complex projects involving main drain lines, water heaters, or gas piping should be left to licensed professionals. Always check local building codes and permit requirements before starting any significant plumbing project.

Why Use This Plumbing Reference Guide?

Having quick access to plumbing specifications helps ensure your projects function properly and meet code requirements. This guide saves time at the hardware store and helps prevent water damage from improper installations.

  • Quickly identify the correct pipe size for any fixture or application
  • Choose the right pipe material (PEX, copper, PVC, ABS) for your project
  • Ensure proper drain slope to prevent clogs and sewer gas issues
  • Understand venting requirements that keep your drains flowing properly
  • Learn proper soldering techniques for leak-free copper joints
  • Know where your emergency shutoffs are located before problems occur
Frequently Asked Questions

What size pipe do I need for a toilet drain?

Toilets require a 3-inch drain pipe minimum, though 4-inch is common for the main drain stack. The toilet's built-in trap connects to a closet flange, which then connects to the 3-inch drain line. This larger pipe size is necessary to handle the volume and solid waste from toilets. Never reduce the size of a toilet drain line - it must maintain 3 inches all the way to the main stack or sewer line.

What is the proper slope for a drain pipe?

Drain pipes should slope at 1/4 inch per foot toward the sewer or septic. This means for every foot of horizontal run, the pipe drops 1/4 inch. Too little slope causes slow drainage and clogs; too much slope (over 1/2 inch per foot) can cause liquids to outrun solids, also leading to clogs. Use a level to check slope before securing pipes. For a 10-foot drain run, you'd need 2.5 inches of drop from start to end.

What's the difference between PEX and copper pipe?

PEX (cross-linked polyethylene) is flexible, easier to install, freeze-resistant, and less expensive than copper. It requires special crimp or push-fit fittings but no soldering. Copper is more durable, heat-resistant, and has a longer track record but requires soldering and is more expensive. PEX cannot be used outdoors (UV sensitive) or for gas lines. Copper can corrode in acidic water. Many plumbers now prefer PEX for residential water supply lines due to its ease of installation and resistance to freezing.

Why does my drain need a vent pipe?

Vent pipes allow air into the drain system, which is essential for proper drainage. Without venting, draining water creates a vacuum that can siphon water out of P-traps, allowing sewer gas into your home. Vents also allow sewer gases to escape through the roof instead of entering living spaces. Every fixture needs a vent, either individual or connected to a main vent stack. Signs of poor venting include gurgling drains, slow drainage, and sewer odors.

How do I fix low water pressure in my house?

Low water pressure can have several causes. First, check if it affects all fixtures or just some - isolated issues point to clogged aerators or supply valves. For whole-house issues, check your pressure regulator valve (PRV) near the main shutoff - it may need adjustment or replacement. Pressure should be 40-60 PSI; below 30 PSI causes problems. Other causes include partially closed main valve, corroded galvanized pipes, or municipal supply issues. A pressure gauge on a hose bib can help diagnose the problem.

Can I use PVC cement to join ABS pipe?

No, you cannot use PVC cement on ABS pipe or vice versa. Each plastic type requires its own specific cement. PVC needs purple primer followed by PVC cement. ABS uses one-step ABS cement (no primer needed). To join PVC to ABS, use a special transition cement designed for both materials, or use a mechanical coupling with rubber gaskets. Some jurisdictions don't allow mixing PVC and ABS in the same system, so check local codes before combining pipe types.

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Most plumbing beyond like-for-like fixture swaps needs a permit.

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