Plumbing has become a lot more accessible for amateurs over the last few years. There are more resources, videos, guides, and information than ever before that can get you up to speed with basic plumbing work. That being said, there are still some homeowners who find the task intimidating and don’t know where to start.
This guide will give you everything you need about bathroom fittings, pipes, and connections so you learn how to plumb a bathroom yourself with confidence. We also recommend getting prices from local plumbers in your area. You can find some free quotes by using the form below.
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Considerations When Plumbing A Bathroom
You want to do your plumbing the right way, and there are a few key aspects you need to consider carefully before starting any work.
Rough-In & Plumbing of Bathroom Components
‘Rough-in’ may not be a term you’ve heard of before, but it's absolutely vital for plumbing. This is the stage of the process where you’ve removed the floorboards, drilled your holes, measured everything out, but you haven't connected up all the pipes and connections. This is your last chance to review everything and make sure everything is correct.
For the rough-in stage, you’ll want to measure up all the fixtures and fittings. There are two key terms you’ll need to understand:
Here’s a rough-in guide to all your key bathroom items.
1. Bathroom Toilets
Bathroom Toilet Rough-In Dimensions:
How To Plumb A bathroom toilet (Step By Step Instructions)
- 1Turn Off Your Water Supply
Use your shut-off valve to stop any water flowing to your toilet so you can plumb it safely.
- 2Install The flange
If installing a new toilet, you'll need to install your flange in the floor. This is what connects directly to your drain. You’ll just need to slot this on the top of the drain and tighten all the screws.
- 3Attach Closet Bolts
Slip the closet bolts into the flange and slip the washers on top. These should point up towards the ceiling. Place a wax ring on top of the flange. This is what will help secure the toilet in place.
- 4Install The Toilet
Carefully lift the toilet into place, so it rests on the flange with the bolts through the pre-drilled holes. Add washers and nuts and tighten, so it’s held in place.
- 5Level The Toilet
Check to make sure the toilet is level and put washers underneath either side if needed.
- 6Attach The Supply Line
The cold water supply line should fit from the wall into the tank of your toilet. Most standard toilets use a ⅜ inch connector, but you may need a different size.
- 7Check It Fills
Switch your water supply back on and make sure your tank fills up and flushes correctly. You may also choose to caulk around the base of the toilet to keep it all securely in place and water-tight.
2. Bathroom Sinks
Bathroom Sink Rough-In Dimensions:
How To Plumb bathroom sink (Step by Step Instructions)
- 1Install Pop-Up Drain
This is the drain cover that will allow you to control when water is emptied from the sink. Drop this into the sink and slide a rubber ring on the underside of the drain. Add a nut and tighten everything in place.
- 2Install Your P-Trap Adapter
You should have a piece of pipe sticking out from your wall. Apply some glue to this drain and attach the P-trap adapter. This will allow you to connect the P-trap.
- 3Attach Your P-Trap
P-traps generally come in a kit. Connect the pipes to form the P shape and fix it with a nut. Put a connector ring over the P-trap adapter and slide the P-trap into place. Tighten the connector to fix it. Add the U-shaped piece of pipe and slide the connector ring over and tighten. This should now connect up to the pop-up drain you installed in step 1. Use a wrench to make sure everything is connected correctly.
- 4Check For Leaks
This is a crucial step. Run your water and check for any leaks. Hopefully, it's all working correctly, and your job is done!
3. Bathroom Shower & Bathtubs
Shower & Bathtub Rough-In Dimensions:
How To Plumb bathtub
- 1Turn Off The Water Supply
Use the shut-off valve to shut off all water to the bathroom.
- 2Mark The Outline Of The Bathtub
Measure up the outline of the bathtub so you can tell roughly where the entrance will be.
- 3Fit The Drain Line
Run the drain line pipe underneath the bathtub and fit it to the bathtub drain.
- 4Fit The Supply Lines
Run the supply lines underneath the bathtub and through pre-drilled holes in your bathtub. This is where your faucet will sit. Remember, you will have one supply line for hot and one for cold. You may need a mixer so you can control the temperature of the water.
- 5Install The Bathtub
Lift the bathtub into place (you may need a friend to help you) and secure it in place. Use caulk to create a water-resistant seal around the edges of the tub.
- 6Fit Your Faucet
Connect your faucet to your bathtub using bolts. Make sure the supply lines are fitted securely to each side of your faucet.
- 7Install The Shower
Connect the pipe from your faucet up about 60 inches from the faucet. Ensure this is connected securely to the faucet and held in place with a clamp or hold it halfway up the wall.
- 8Connect The Showerhead
Connect the showerhead to the shower pipe.
- 9Test The System
Turn the water bath on and make sure it’s all connected and working without any leaks.
Not convinced that you want to do this all yourself? Get a free quote below.
The DWV System (Drain, Waste & Vent) For Plumbing Bathrooms
The DWV, or drain, waste & vent, plumbing system is used in most modern bathrooms. It’s an efficient plumbing system that allows you to keep even air pressure in your plumbing system. This allows all waste to flow freely through the pipes and drain more easily.
Plumbing a basement bathroom isn’t an easy job. It will often involve breaking through concrete and taking on heavy-duty work to make it a success. For this work, you’ll need:
Here are the steps you need to take:
- 1Locate The Main Stack
The main stack is the main drain pipe that runs down into the basement. This is typically 3-4 inches wide, and you'll need to look for a cleanout plug on the exterior wall. You’ll need to break through the concrete in the floor to make sure it’s there.
- 2Plan Your System
Plan out your bathroom system on the floor, including all the different fixtures and the drain lines. Draw these on the floor and use masking tape to mark them out.
- 3Trench The Floor
Use a sledgehammer to start breaking through the floor along the main drain line. Remove the larger pieces of concrete and keep the dirt to refill the hole later on in the process.
- 4Break Open A Section Of Drain
You’ll need to open up the main drain so you can install a Y fitting. This will allow you to connect your bathroom fittings to the drain supply.
- 5Build Your Drain System
You’ll need to start building out your drain system for each of your fixtures. Break open the floor and lay the drain pipes to the toilet, shower, sink, and bathtub as needed. Put caps on the pipes as you go, so none of the sewage gas escapes into the basement.
- 6Seal The Floor
With your drains fitted, you can seal up the floor. Put the dirt back into the holes and lay fresh concrete over the patches. Make sure everything has dried before moving to the next step.
- 7Build Your Vent System
Your vent lines should align to your bathroom walls and sit along your ceiling. Assemble the vent lines and connect them into an existing vent using a T or Y fitting, which should be cut into your venting system.
- 8Position Your Shower Drain
Your shower drain will need to be lower than the others in the floor and sloped at ¼ inch per foot. Set the shower pan and drain in place before installing all the different components and sealing everything up. You should now have a fully fitted DWV plumbed bathroom in your basement that works perfectly.
New Bathroom (with Existing Plumbing)
Upgrading your existing plumbing to make it more modern and effective isn’t as difficult, but will still require some work. To fit the DWV system, you’ll need to add a few different parts to your fittings.
You’ll then need to follow these steps:
- 1Vent The Toilet
Your toilet should ideally fit to your main stack, but you'll need it within 6 feet of this for it to work. The best way to vent the toilet is to connect it to the sink drain so it can operate as a wet vent. You’ll need to make sure the toilet is less than 6 feet from the sink for this to work.
- 2Connect Your Fixture Drainage
Your bathtub, sink and shower all need to connect to your waste and venting system. They all need to plumb into your sewage system and the main vent stack. The easiest way to do this is to connect all of your plumbing into one central pipe. This should be located higher than all the fixtures and then attach to your main vent. Your drains can remain separate or joined up. Ensure that all drainage is sloped at ¼ inch per foot towards the drain outlet, and the vent slopes up ¼ inch per foot away from the drain.
- 3Replace The Pipes
While you’re thinking about re-plumbing your pipes, you should consider the type of pipe you use. PEX is the modern alternative that works well for DIYers because it’s affordable, durable, and really flexible. These are the most straightforward to use, and you should look to replace all the different copper or galvanized metal pipes with PEX if possible.
People Also Ask (FAQs)
Is it hard to move the existing plumbing in a bathroom?
Yes, relocating your plumbing is arduous work and needs careful planning. You should allow at least a few weeks to complete the work.
Can you use a pex pipe in bathroom plumbing?
Yes, PEX is a more modern type of pipe that is more affordable and extremely durable.
Can a toilet and shower share the same drain?
Yes, though you need to be careful to make sure they have different waste trap arms.
How many bends can you have in a drainpipe?
Having more than one 90 degree bend in your drain pipe can cause blockages and other issues, so it isn't recommended.
Does a P trap have to be directly below the drain?
Having a P-trap directly below your drain can cause issues because gravity can force the water straight through the drain. It’s typically better to have them at a slight angle.
Can a plumbing vent run horizontally?
Yes, as long as it is sloped correctly so it won’t become plugged with water.
Plumbing a bathroom sounds challenging, but it’s really not. You need to consider your drainage and venting systems and plan them out clearly from the start. This will then allow you to consider each fixture one by one and get them right.
Hopefully, this article has given you the information you need to get started with confidence.
Holly Curell is the editor extraordinaire for Plumbing Lab. Having grown up in Michigan, Holly has spent time living in New York, Virginia, & currently North Carolina, where she lives with her husband & family. Holly loves DIY & has years of experience with at-home plumbing problems that arise from having 3 kids & living in colder climates. When she’s not writing about her plumbing knowledge, Holly enjoys reading, hiking & relaxing with family.