A tile shower pan is one of the great mysteries of home repair or construction. Anything to do with tile showers is usually left to the pros. There's a reason for that too! But sometimes handy people install showers themselves once they see the mysteries revealed.

See the real tile shower trick is hidden beneath the floor. You can't see the tricky part from the top of the shower or from underneath for that matter. Not too long ago my tile shower started leaking. Water had soaked the hardwood floor in the bedroom. That's how I noticed. I finally saw the cracked grout down near the floor, but I thought there was a shower pan under the shower so why was it leaking?

Here's the scoop.

Tile floors are not waterproof. Water seeps right through tile shower floors, mostly through the grout. Grout is porous masonry so water slowly soaks the grout and then goes through it. That's why you need a shower pan. See the shower pan is actually a waterproof liner below the surface of the floor that catches the water.

But then where does the water go from there?

Ah, there's another trick. A tile shower drain is a special design with two layers of drain holes. The bottom drain layer is actually below the floor, and that's the one the waterproof layer sends the water to. So the shower pan is built in three layers so all the water is captured and routed down the drain.

Three layers?

The bottom layer is sloped masonry built over the subfloor or concrete. The bottom layer slopes to help send the water toward the drain. The top of the bottom layer is flush with the bottom drain holes. The second layer is the waterproof liner which is a tough vinyl sheet that's glued to the drain base to make a waterproof pool to catch all the water that seeps through the floor. The top layer is another masonry layer that's poured and sloped above the liner. This is the base for the shower floor.

That's the trick to a shower - the sloped layers and liner route the water to two layers of drain holes. If the waterproof membrane fails or if it isn't installed properly , the shower will leak. As you probably know, shower floor leaks can be very expensive. It really makes sense to get a shower pan done right.

Now you have other choices when building a shower. Several materials can be used for bases, but the traditional construction is hard to beat for price and performance. Plus you can learn to do it yourself if you want to.

So the real mystery to a tile shower is the special drain. The drain has a bottom layer of drain holes that you can't see. A waterproof liner is built into the shower floor and catches all the water that may seep through the shower floor. When your shower leaks the waterproof liner has probably failed.