How-to-measure-bathtub-drain-size

How to Measure Bathtub Drain Size

If you’ve bought a new bathtub like freestanding or air bathtub or you’re renovating your bathroom, the process is never complete without installing a new drain and overflow assembly.

Before installing the bathtub, you have to measure bathtub drain size so that you can choose the right set for your bathroom. Sometimes, you only need to measure the old drain and overflow assembly, but if you’re trying something new, you’ll have to measure it yourself.

Steps to Measure Bathtub Drain Size:

1. Drain & Overflow Assembly

If you’re new to renovations in the bathroom, you might not be overly familiar with what this assembly is. Before the steps on how to measure the tub drain size, here a little explanation on the drain and overflow assembly.

The unit is an L shaped assembly. It is made up of the drain fitting which is fitted into the gap at the bottom of the tub, which connects to a drain pipe that leads to the tee fitting.

The drain is connected to the drain pipes underground, and the overflow is meant to prevent flooding in the bathroom. There’s a high chance that your bathtub includes an overflow, but if it doesn’t, there’s no need to worry.

Tools Needed:

  • Plumbing measuring tape.
  • Paper and pen.
  • Large adjustable wrench.
  • Channel-lock pliers.
  • Lubricant.

As long as you follow these few steps on measuring bathtub drain, you will get the right fit for your new drain and overflow unit. You have to know how to reach the plumbing areas that you want to measure before you can take your measurements.

  • Step 1

With a tape measure, measure the drain hole in the tub. This would be the width of the drain pipe. Remember to write the measurements down as you measure bathtub drain size.

  • Step 2

Next, you have to detach the plumbing access panel. You can find this behind the wall where the faucet fixtures are. Take note that when you remove this, you have to be careful because you might damage the wall.

If you don’t have the access panel, the only way you can get to the drain and overflow assembly is by breaking in the wall or the floor, and this needs to be done by a professional. After measuring, you should install a new one for future purposes.

  • Step 3

Find the drain pipe and overflow pipe, and the plumbing that is installed for it.

If the Old Drain Pipe is Still in Place

It’s easier to learn how to measure tub drain size if the old drain pipe is still attached.

  • Step 4

Detach the previous drain pipe. You can do this by using either the large adjustable wrench or the lock pliers to loosen the bolts from the strainer device and pipe. If the bolts are too stiff, you can use the lubricant before loosening them.

  • Step 5

Using your tape measure, get the horizontal and vertical measurements of the previous drain pipe. This would stand as the length and width, respectively, of your new drain.

If The Old Drain Pipe is No Longer Attached

It might be much more difficult measuring bathtub drain if you can't directly measure the old drain pipe. But, you can follow these steps if that is the case.

  • Step 4

Stay leveled to the floor so that you can measure the space where the old drain pipe used to be. Using your tape measure, measure the bathtub drain hole, straight down to the plane where the plumbing pipe is divided into two directions. That would be the measurement of the vertical space between the drain hole and the plane where the plumbing pipe branches off.

  • Step 5

From the panel where the plumbing pipe branches off to the drain on top of the drain hole, take the horizontal distance measurement. The vertical distance measurement will act like the width while the horizontal distance measurement will be the length of your new drain. When you take this to the hardware or home improvement store, you will get a drain that fits the measurements.

  • Step 6

You can also decide to measure the height and depth of your bathtub. Take the measurements from the top rim of the tub to the bathroom floor. You might not need this when choosing your new drain unit, but it might come in handy.

2. Connecting the New Drain

  • Step 1

Using the large adjustable wrench or lock pliers, attach the new bathtub drain tightly to avoid leakages.

  • Step 2

After connecting it, put on the plumbers putty and ensure that it is tight so that it won’t leak.

  • Step 3

Tighten the strainer. Test the new drain by running water through the drain before you place the plumbing access panel back on the wall. Ensure everything is sealed properly.

Standard Bathtub Drain Size

If you don’t think you can measure bathtub drain size, you can always go for the standard dimensions although this is risky. The standard drain size of a modern bathtub is 1 ½ inch in diameter.

The width is direct across the middle. Thus, the plumbing should be measured based on a 1 ½ -inch pipe. If you use a clawfoot tub, it might be around 1 3/8 inches in diameter.

It is advisable to go through the process of measuring your drain size directly so that you don’t make mistakes in your purchases. Keep in mind that bathtub drains are either made of plastic or brass.

If you want something more durable, you should buy the brass drains although they are more expensive than the plastic.

Why You Need the Right Drain Size

When measuring bathtub drain, it's important to get the right size. The bathtub drain and overflow assembly, and the drainpipe with all its fixtures are all connected as the home's overall system.

If the drainpipe gets clogged because they are too small for the amount of waste going through them, the other parts of the system and the fixtures can end up with backed up water.

This can also affect the toilet. When water backs up in your drainpipe, dirty water can come out of your bathtub and toilet, and it would require the expertise of a plumber.

Last Words

Now that you know how to measure tub drain size, you can get to it immediately. As long as you have the right tools, you can get it done under half an hour if it all goes according to plan.

You can visit your local hardware store or home improvement store to get the tools you need and the type of bathtub drain that you want to install.

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