How To Rough in and Install Bathtub Spout Like a Pro

Roughing in a bathtub spout is an intimidating job if you’ve never done it before. However, with a good drill, sealant, and the right boring bits, nearly anyone can do a great job. In fact, your tub spout rough in shouldn’t take more than a few hours, especially if you’ve already bought the plumbing. Chances are, you’ll also have to do less roughing in than you think – unless you’re installing a completely new tub and wall.

A bathtub faucet rough in means drilling holes in the wall to run pipes from the water line to the tub spout. Plumbing your tub spout mostly requires taking good measurements, drilling in the right places, and keeping the holes as small as possible. This both prevents structural damage and reduces the need to seal around the faucet.

How to Rough in a Bathtub Spout

Roughing in a bathtub spout is the process of boring holes in the wall, studs, and frame and running water supply through those holes. This normally involves a rough process of laying out pipes, cutting holes, and fitting the plumbing into the wall. In this guide, we’ll cover each step in order, including basic safety to ensure your wall remains sturdy. In this case, the instructions are only for roughing in the water faucet. That means the water lines from the main water supply to the tub and the holes for the faucet.

Make sure your water is turned off to the bathroom before doing any work involving pipes or water lines. You might also want to consider draining any excess water into the sink or toilet to prevent leaking on the floor. 

What You’ll Need

You’ll always need the following tools:

  • Tape measure
  • Pencil or chalk line (preferably blue chalk)
  • Level
  • Drill with a Forstner or spade bit set, at minimum 5/8ths Forstner bit and ½-inch Forstner bit
  • Drill set compatible with your faucet, usually Phillips #2
  • 3/8ths ABS or PVC pipe. Check what’s already in your bathroom + fittings to connect to the main line.
  • Y connector/reducer
  • Pipe cement
  • ½-inch male pipe connectors
  • The faucet
  • Hammer
  • Phillips #2 screwdriver
  • Flat screwdriver

Find the Main Line

The first step to installing your bathroom faucet is to figure out where you’re connecting it to the water lines. In this case, you have to find the hot water line and the cold-water line. If you’re replacing an old faucet, those pipes are already in place. If not, you might have to run them a significant distance to the new tub location.

  • Use a tape measure to measure the distance between the main line and the faucet connection. Make note of any corners and be sure to buy appropriate elbows for these turns. You want to install pipes inside the wall to keep them out of sight. Measure the distance of each length in between turns.
  • Check if the main line already has a Y or split off of it. If not, you’ll have to turn off the main water and connect a T. Check the size of your main water line. Normally, it will be ¾ inch or 1 inch and you’ll want to reduce it to 3/8ths.
  • Check the connections on your faucet. Most use a 3/8ths inch connector. Some need a ½ inch connector or adapter. You’ll almost certainly need a male connector. However, this is not universal. Make sure you check.
  • Buy your pipe and fittings based on these measurements.
  • You need two lines. One from the hot water source and one from the cold-water source. Normally, it’s a best practice to find the closest mains pipe to the new faucet and divert the line from there.

2. Decide Where You Want Your Faucet

Take your faucet and decide where you want it in the bathroom. Measure where the fitting should be, use a level to ensure it’s flat, and mark the spot with blue chalk, pen, or marker. Use a marker that you cannot rub away to trace around the fittings on the back. You will drill here.

3. Cut and Lay Out Pipe

Remove the baseboards along all walls that require pipes. Use a flat screwdriver and a hammer to pry the drywall up and take care not to damage it. Then, measure the exact distance inside the walls. Cut your pipes to match these lengths. Line them up along the wall to the faucet.

Here, it’s also a good idea to check that your wall studs are large enough to drill in. If not, you’ll have to buy extra wood for support. According to the 2012 International Residential Code Book, pages 159 and 160, holes in load bearing wall studs must be no more than 40% of the width and balanced to the center of the beam. In this case, your wall studs should be at least 2” wide. Because most wall studs are 6” wide, you should have no problems.

4. Drill Holes

Check the minimum size your ABS or PVC pipe will fit through. If you’ve bought 3/8ths pipe, you’ll usually need a 5/8ths spade bit. That’s because the ends flange or flare out. If they don’t, you can go for a smaller hole.

Use a bit appropriate for ceramic or tile for your bathroom if you’re drilling in a tile wall. In addition, make sure you check the backing on the tile. If the wall is tile with no backing, add support for when you drill. You can do so by cutting a 2×6 to fit between the wall studs at the level you want to drill. Use screws to attach it to the wall stud. Then, when you drill the tile, the weight distributes onto the backing support so that you don’t crack the tile.

Drill all holes and check that your plumbing fits in.

5. Fit the Faucet

Drill holes for the faucet using a Forstner or Spade bit. Here, you want to use the smallest possible bit that the faucet fittings will go into. The more snug the hole, the less chance of leakage. In addition, the valve fittings keep the faucet attached to the wall. Using smaller holes makes it more difficult for the faucet to come loose at a later point in time. In most cases, the bit should be about ¼ to ½ inch larger than the nipple inserted through the wall. That usually means a 5/8ths Forstner bit is perfect. However, this will change depending on the faucet because there are no standardized sizes.

Importantly, if you’re using a one-piece faucet, you have to trace all of the holes together and drill them. That will mean drilling the center line and the holes for the valves. If you’re installing a tub spout with separate knobs or valves, drilling holes is more complicated. You’ll have to decide on a distance between the tub spout and valves and then use a level to make sure everything is level. Most new faucets come with guide or stencil to determine the distance for you. If you have an older faucet and don’t have a guide, try to center the valves 2.75 inches away from the center of the faucet. 2.5 inches is the recommended minimum distance between the faucet and the tap.

6. Glue Everything Together

Once you’re certain that everything lines up and fits well, glue everything together. Use pipe glue matching the pipes you bought. That may be ABS or PVC. You may also want to use copper lines for hot water. However, it shouldn’t be necessary.

This is the most time-consuming part of plumbing a tub spout because you’ll usually have to let glue dry for at least 24 hours before running water through it.

How to Install a Tub Spout

Once you’ve roughed in your tub spout, you can move on to tub spout installation. With the holes roughed in, this process is relatively simple and should not take more than half an hour. Luckily, bathtub faucet installation is relatively easy to professionalize.

Unfortunately, there are two different tub faucet installation types. We’ll go through both.

You Will Need:

  • Caulk and a caulk gun
  • A Phillips #2 Screwdriver or a Regular Flathead screwdriver (Check your taps)
  • Adjustable wrench
  • Rags or cleaning solution
  • A measuring tape
  • If possible, the installation manual for your faucet
  • P.T.F.E. tape
  • The installation guide from the faucet spout

1. Attach the Tub Spout

Your tub spout should attach to the wall with the nipple for the spout inserted 3/8ths to ¾ of an inch past the finished wall. You screw the pipe adapter onto this – which attaches to the water lines.

Alternatively, if you have a valve and faucet set, it likely attaches to a trim plate. This installs behind the wall and the valves screw into it. With enough tension, the valve and faucet are held firmly against the wall. On the other hand, if your faucet and valve set does not come with a trim plate, you can always screw a 2×6 into the space between the wall studs to perform the same function. However, you’ll have to pre-drill holes, ensuring that they line up with the holes in the tile.

2. Connect the Water Lines

Connect the water lines from the faucet to the wall. Normally, this should involve screwing the nipple on the faucet into the male connectors you attached to the plumbing. However, if you have flexible metal water lines at the end, you can make these attachments with the faucet pulled out from the wall. On the other hand, if you don’t, insert the faucet and valves into the holes you drilled in the wall. In addition, if you have a separate faucet and valve set, the nipple will install from the back of the wall and you’ll stabilize it using the copper tubing that runs through the wall.


  • Wrap a line of P.T.F.E. tape around each nipple twice. Break it off.
  • Screw the male attachment tightly onto the nipple using your hands. Make sure the threads go on straight.
  • Tighten the male attachment as far down as you can.

In addition, if you have a separate tub spout and valve set, you’ll have to run copper tubing through the wall. You’ll attach the tub spout to this.

3. Attach the Spout

Attach the tub spout. Here, you’ll either simply tighten the screws in the valves or simply slide the tub spout over the copper tubing. Make sure everything fits and that with the spout firmly in place, you can’t see any holes. Then, take everything off again.

4. Caulk the Holes

Use caulk to seal the holes around the valves, the plumbing coming through the wall, and the seal between the spout and the wall. Put the spout back on. You can then tighten any screws for the spout or valve as instructed on the package and allow the caulk to dry.

Unfortunately, there are many different types of shower and bathroom spouts. In some cases, you’ll have to install a support ring or a screw plate. Here, you’ll attach the plate and then screw or snap the fitting onto it. Luckily, this will always come with instructions on the box and you can always go to the manufacturer’s website for more information.


If you still have questions, this FAQ should help.

Should I caulk around a tub spout?

Yes. It’s important to seal around your tub spout as well as you can to prevent leaks. For example, caulking your tub spout keeps water out of the inside of the mechanism. Therefore, this will prevent rust and possibly prevent molding or water damage inside the wall.

Can you use SharkBite for tub spout?

Yes. SharkBite is an extremely popular plumbing manufacturer. For example, the brand’s push-to-connect fittings can simplify installing your tub spout. However, you’ll still have to ensure you get an appropriate male fitting to connect to the nipple on the faucet and valves.

What do you do if your tub spout is too short?

The best solution to your tub spout being too short is to buy a longer tub spout. However, if that isn’t an option, you can extend the wall around the tub spout. Here, you should build a wood box of the appropriate length, drill holes for the faucet, and then install the faucet into that. It’s usually a good idea to tile or waterproof the wood box to prevent water damage.


Professionally roughing in and installing a tub spout can take some time. That’s especially true if you have to run water lines more than some distance. It’s also important to ensure that you’re using appropriate water lines. For example, some regions mandate using copper lines for hot water. Check your local building code. In most areas, ABS or PVC lines are more than enough. In addition, the exact final installation steps will always depend on your specific faucet. Make sure you adjust steps based on the exact measurements of the faucet.

Good luck with roughing in your tub faucet.

Recent Posts