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Tub Shower Valve Mistakes and How You Can Avoid Them

In this tutorial, you’ll see common tub shower valve mistakes and how to avoid them.

Unfortunately, many people install shower valves incorrectly. T

his causes water leaks and ugly tile installations.

Today, you’ll learn how to avoid common mistakes and get a step-by-step plan that makes your tub shower valve installation easy and gives you beautiful results in the end. 

Let’s dive in!

How to Choose the Tub Shower Valve

The first big mistake homeowners make is choosing the wrong valve.

Your shower valve ought to last a very long time.

Delta Tub Shower Valve

Sadly that’s not the case if you buy the wrong one.

I don’t recommend cheap valves from Amazon…

Or local home stores.

Instead, buy shower valves from plumbing supply houses.

I buy my from or 

In addition, sticking with brand names is a good long-term investment.

For instance, Delta shower valves warranty the cartridge, tub spout, escutcheon, and shower head. 

Over time, this can save you a lot of money and aggravation.

Furthermore, the better the valve the more likely the trim finish will last.

Shower Valve Trim

Nobody should have to buy a new trim kit after only a few years.

But this is the risk you take when buying a cheap Amazon valve. 

Here’s a pro tip for tub shower valves, 

Get valves with the copper stub out pre-installed.

Delta Tub Shower Valve for PEX B

This saves you time and you won’t have to solder copper to the bottom port.

Plus, you can be sure the copper stub out will be centered on the tub drain.

Trust me, this is a huge advantage you’ll appreciate during the installation.

Also, get a valve that has the proper fittings.

This Delta R10000 valve can be bought with PEX A or PEX B barbed fittings. 

Delta Tub Shower Valve with PEX B

And this means you don’t have to thread fittings on for PEX tubing. 

Once again, this saves you time and money from the get-go.

So, choosing the right valve from the start’ll speed up your installation…

And make your life a lot easier.

However, you need to avoid the next three mistakes to make it through your project unscathed 

Shower Valve Depth

The second biggest mistake is setting the shower valve to the wrong depth

Unfortunately, this isn’t as straightforward as you’d think

And definitely, something even some contractors might overlook

Remember this important principle,

Shower valve depth is critical for the tile shower wall. 

Shower Valve Depth for Tile

If the valve is too deep you might not be able to put the trim on.

And if the valve is too shallow, the trim will bottom out

Both situations would be very frustrating 

Primarily, since it’s almost the last step in a tile shower.

So you don’t want to make this mistake.

I always consider the backer board orientation before setting the valve.

For instance, in this shower, I had to add 3/4” strips of plywood to the studs.

This helped me bump out the wall…

and place the KERDI-BOARD on top of the tub flange.


By the way, if you’re wondering, the board can be above the flange.

I waterproofed it to the tub using thin-set, KERDI-FIX and KERDI-BAND.

But the details of how I did that are for a different tutorial.

The bottom line is this, you need three things to set the valve to the right depth.

First, you need to know the shower backer board thickness.

I was using 1/2 inch KERDI-BOARD, so that was easy to figure out.

Second, you need to know the tile shower wall thickness or have a tile sample

And finally, you need to guesstimate the thin-set thickness of the tile.

Any tiles less than 3/8 inch thick will probably use at most 1/8 inch of mortar.

But if you dry-fit the backer board & tile on the studs, that’ll help you set the valve depth.

I normally use either a 2×4 or 2×6 for tub shower valves.

Shower Valve Depth

I draw lines on the studs with my speed square. 

Then secure the 2×4 to the studs with two 3-inch construction screws.

I use two screws on the left and two screws on the right.

Then I double-check check the valve is at the right depth.

I dry-fit the backer board and tile against the plaster guard.

And if those are even or within 1/8” I know the valve is at the correct depth.

Once the valve is at the right depth, the next step is determining the height.

Shower Valve Height

The third biggest mistake homeowners make has to do with shower valve height.

I always get asked, how far above the tub should a shower valve be?

The answer the copper tub spout should be about 4 inches above the tub deck.

Now here’s the deal, 

The Delta shower valve with the copper tub spout pre-installed makes this easy.

I place my tape measure on the tub deck.

Raise the copper tub spout to 4 inches.

And there you go, that’s the proper height of the valve.

Shower Valve Height

4 inches is a good height because of the tub spout.

It ensures there will be enough room between the bottom of the spout and the tub.

So that when you twist the spout onto the adapter, the spout won’t hit the tub.

Yet it also won’t look too far off the tub deck.

Tub Spout Height

Once the shower valve height and depth are established, the next step is plumbing.

And that’s where you don’t want to make any mistakes.

Rough In Shower Valve Tips

The fourth big mistake homeowners make with shower valves is plumbing connections. 

Here’s a common question I get, can I use PEX for shower plumbing?

Yes, PEX A or PEX B can be used for tub shower valves. 

But only copper should be used for the tub spout. 

Delta Tub Shower Valve with PEX

And that’s one reason I love the Delta valve with the copper already installed.

That said, it’s perfectly acceptable to use PEX for the hot and cold water supplies.

I’m a big fan of PEX A because it’s more flexible than PEX B.

This is a big advantage for tight stud bays like in this shower. 

PEX a vs PEX b

You can see how I can bend the PEX A without needing a 90-degree fitting. 

That said, the first plumbing mistake is kinking the PEX and still using it. 

Kinking PEX A

You can bend the PEX but if it kinks you have to cut out that section. 

I use either Schluter ALL-SET or unmodified thin-set mortar to bond KERDI-BAND.

This ensures my mortar will bond to the fleece on the pan, walls, and banding. 

The second plumbing mistake is not cutting PEX properly.

I always make sure the PEX is cut square.

How to Cut PEX A

That way it’ll fit tight against the shower valve fittings.

The third plumbing mistake is using the plumbing tools incorrectly.

I used ProPEX rings with PEX A in this shower. 

And for 1/2 inch PEX A, I can expand the ring and tube 5 to 6 times.

Then I immediately push the ring and tube onto the valve fitting. 

I ensure the ProPEX ring is snug against the shoulder of the fitting.

Delta Shower Valve with PEX A

And I hold it there for 10 to 15 seconds. 

Once I have the hot and cold water supplies installed, I do the riser pipe.

Frequently I get asked if the riser pipe can be PEX…

And the answer is yes because this valve has a PEX A fitting on the top.

I use a 1/2” drop ear and place that at about 85 inches off the subfloor.

The fourth plumbing mistake is not making the blocking plumb for the drop ear.

I check this using an 8” level.

Shower Drop Ear

It’s important to have this drop ear plumb so that the shower arm is level for the shower head.

The fifth plumbing mistake is not centering the drop ear on the valve.

I always find the center of the tub and place the drop ear at that dimension

Centering Drop Ear

Then I screw the drop ear to the blocking and get a measurement for the riser.

This makes the riser pipe installation a lot easier.

I add the riser pipe to the valve first.

Again, making sure the ProPEX ring is against the shoulder of the top port.

Then I remove the riser pipe from the blocking and install the PEX A.

PEX A for Drop Ear

And secure the drop ear back onto the blocking.

The sixth plumbing mistake is not securing the copper tub spout if it’s loose.

I added wood blocking just below the valve.

Then I used a copper tube strap to secure the copper tub spout.

This makes the tub spout super secure so that it won’t ever wiggle inside the wall.

What’s Next

Tub shower plumbing can be daunting if you’ve never done it before.

And it’s just one phase of tub shower renovation.

If you’re remodeling a bathroom and need help, join our Platinum Membership.

I promise the step-by-step tutorials and Personal Coaching will make your project easier.

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