To join two drain pipe sizes, use a DWV increaser-reducer; to reduce inside an existing drain fitting, use a DWV flush bushing; on water lines, use a Schedule 40 pressure reducer bushing. Charlotte Pipe says its Schedule 40 fittings are for pressurized liquids only, so do not mix DWV and pressure reducers.
Plumbing Picks is reader-supported. As an Amazon Associate, we earn from qualifying purchases at no extra cost to you.
This guide covers PVC reducing fittings for drain and pressure piping.
PVC reducers at a glance
| Reducer | Ends | Use it when |
|---|---|---|
| Increaser-reducer (DWV) | Hub x hub | Joining two different drain pipe sizes end to end |
| Flush bushing (DWV) | Spigot x hub | Reducing inside an existing drain fitting hub |
| Reducer bushing (Sch 40 pressure) | Spigot x socket, or MPT x FPT | Reducing water or other pressure lines |
A PVC reducer joins a larger pipe or fitting to a smaller one. The first question is not the size but the system: drain, waste and vent (DWV) fittings and Schedule 40 pressure fittings look alike but are made for different jobs. Charlotte Pipe notes (charlottepipe.com) its Schedule 40 fittings conform to ASTM D2466 and are for distribution of pressurized liquids only, with operating temperatures not over 140°F.
DWV increaser-reducer: hub x hub
Use a DWV increaser-reducer to join two drain pipes of different sizes. Charlotte Pipe’s DWV fittings catalog (charlottepipe.com) lists its Part No. 102 pipe increaser-reducer with hubs on both ends in sizes such as 1-1/2 x 2, 2 x 3 and 3 x 4 inches, in PVC and ABS. Both pipes glue into hubs, so the joint is a smooth, sloped transition rather than a sharp step.
On October 15, 2026, the standard new offer from a third-party seller showed stock with a Charlotte Pipe 2 x 3-inch PVC DWV increaser-reducer, part PVC 00102 1000HA.
Check Charlotte Pipe 2 x 3 in. PVC DWV increaser-reducer on Amazon →
DWV flush bushing: spigot x hub
Use a flush bushing when you need to reduce inside an existing fitting. Charlotte lists (charlottepipe.com) its Part No. 107 flush bushing as spigot x hub: the spigot end glues into the larger fitting’s hub, and the smaller pipe glues into the bushing. It takes almost no length, which helps in tight spots like under a sink or inside a wall.
Check the direction of flow in drain lines. Plumbing codes generally do not allow a drain to get smaller in the direction of flow, so in drainage, bushings are usually used where a smaller branch or fixture line connects into a larger fitting. Ask your inspector if you are unsure.
Schedule 40 pressure reducer bushings
Use a Schedule 40 pressure reducer bushing on water lines and other pressure piping. These come as spigot x socket (glue on both ends) or as threaded MPT x FPT. Charlotte’s Schedule 40 submittal (charlottepipe.com) lists socket dimensions by size for its pressure fittings, and notes the system is intended for pressure applications at up to 140°F, with fittings made from cell class 12454 PVC compound and conforming to ASTM D2466.
On October 15, 2026, the standard new offer from a third-party seller showed nine left with a Charlotte Pipe 2 x 1-1/4-inch Schedule 40 PVC reducer bushing, MPT x FPT, part PVC021123800.
Check Charlotte Pipe 2 x 1-1/4 in. Sch 40 PVC reducer bushing MPT x FPT on Amazon →
For a glue-on version, the listing describes the NIBCO 4518 as a 1-1/2 x 1-inch Schedule 40 PVC reducer bushing, spigot x socket. On October 15, 2026, the standard new offer from a third-party seller showed stock with model 837-211.
Check NIBCO 4518 1-1/2 x 1 in. PVC reducer bushing on Amazon →
Bushing or reducing coupling?
A bushing fits inside a larger fitting’s socket or hub, so it saves space and lets you reduce at an existing tee or elbow. A reducing coupling, like the DWV increaser-reducer, connects two pipe ends and adds a short length of fitting between them. When you are joining two straight runs, a reducing coupling is simpler. When you are reducing at a fitting you already have, a bushing avoids adding another joint.
Stacking bushings to make a big reduction adds joints and can create a rough flow path. Use the single fitting sized for the reduction you need.
Do not mix DWV and pressure fittings
DWV fittings have sweeping turns and are made for gravity drainage, not pressure. Schedule 40 pressure fittings are made for pressurized water. Charlotte states its Schedule 40 fittings are for pressurized liquids only. Do not use a DWV reducer on a water supply line, and use the fittings your code and the pipe maker specify for drains. Our PVC pressure fittings guide covers pressure fittings in more detail.
Threaded reducers: tape and torque
A threaded MPT x FPT reducer bushing lets you step down to a smaller threaded fitting or valve. On plastic threads, use thread seal tape or a sealant rated for plastic, and do not overtighten: hand-tight plus one to two turns is a common guideline, but follow the fitting maker’s instructions. Overtightening a plastic female thread can crack it. Our PVC male adapter guide covers threaded transitions, and our PVC cement guide covers the glue joints.
Gluing PVC reducers
Cut the pipe square, deburr it, dry-fit the joint and mark it. Apply primer where your local code requires it, then cement to both the pipe and the fitting socket, push together with a quarter turn and hold for a moment so the joint does not push back out. Our purple primer guide explains when primer is required.
PVC and ABS need different cements, or a transition cement made for joining the two where your code allows it. Our PVC vs ABS guide covers the differences.
Sizing a drain reduction
Common sizes. Charlotte’s DWV catalog lists increaser-reducers from 1-1/2 x 2 inches up to large commercial sizes, with 1-1/2 x 2, 2 x 3 and 3 x 4 inches the sizes most homes use: a fixture drain stepping up to a branch, or a branch stepping up to the main. Pressure reducer bushings come in nearly every combination of standard pipe sizes, so order by the exact two sizes printed on the pipe, not by eye.
Drain sizes are set by the fixtures they serve, not by convenience. Before you reduce a drain line, check the trap and drain sizes required for each fixture; our trap size by fixture guide covers common sizes. If you are joining to a different pipe material, such as cast iron or clay, a flexible or no-hub coupling may be the right part instead; see our no-hub vs Fernco guide.
Frequently asked questions
What is the difference between a PVC bushing and a reducing coupling?
A bushing fits inside a larger fitting’s socket or hub; a reducing coupling joins two pipe ends of different sizes.
Can I use a DWV reducer on a water line?
No. DWV fittings are for drainage; Charlotte says its Schedule 40 pressure fittings are for pressurized liquids.
What is an increaser-reducer?
A DWV fitting with hubs on both ends that joins two drain pipes of different sizes; Charlotte lists it as Part No. 102.
Can I reduce a drain pipe size?
Reducing in the direction of flow is generally not allowed in drainage. Check with your inspector.
How tight should a threaded PVC reducer be?
Hand-tight plus one to two turns is a common guideline; follow the fitting maker’s instructions and avoid overtightening.
How we chose
This document-based guide makes no hands-on testing claim. We read Charlotte Pipe’s DWV fittings catalog, its Schedule 40 pressure product page and its Schedule 40 submittal. The NIBCO bushing is described from its listing. On October 15, 2026, all three linked standard new offers came from third-party sellers and showed stock. Read our selection method and about Plumbing Picks.
Primary sources
- Charlotte Pipe PVC and ABS DWV fittings catalog (charlottepipe.com): Part 102 increaser-reducer, Part 107 flush bushing, sizes.
- Charlotte Pipe PVC Schedule 40 pipe and fittings (charlottepipe.com): ASTM D2466, pressurized liquids only, 140°F.
- Charlotte Pipe PVC Schedule 40 submittal (charlottepipe.com): socket dimensions, cell class, scope.