Installing a Black Linear Shower Drain: Common Mistakes
By Maintenance Depot Plumbing Team · Last reviewed
Quick answer
The most common mistakes with linear drains like the Bisman 18" matte black BMFD18AMB are forgetting the 2" flange, not levelling the drain, weak waterproofing, the wrong floor slope and damaging the finish during tiling.
Linear drains like the Bisman 18" matte black linear drain (BMFD18AMB) make a shower look great, but a few common mistakes can lead to leaks, pooling water or a drain that sits too high. Here's what to watch out for.
Specs at a glance
| Spec | Detail |
|---|---|
| Product | Bisman BMFD18AMB linear drain |
| Size | 18" x 2-3/4" |
| Levelling | Adjustable feet |
| Recommended floor slope | About 1/8" to 1/4" per foot toward the drain |
| Flange | 2" ABS, PVC or cast iron (sold separately) |
1. Forgetting the drain flange
This drain fits 2" ABS, PVC or cast iron flanges, but the flange is not included. Buy it with the drain so the job isn't held up.
2. Not using the levelling feet
The drain has adjustable levelling feet. Take time to set it perfectly level and at the right height, usually just below the finished tile surface. A drain that's out of level will hold water at one end.
3. Poor waterproofing
Most shower leaks happen around the drain. Follow your waterproofing membrane maker's instructions closely and seal the joint between drain and membrane.
4. Wrong floor slope
Slope the floor in one direction toward the channel, about 1/8" to 1/4" per foot. Too flat and water pools; too steep and it feels uneven underfoot.
5. Scratching the finish
Protect the matte black grate during tiling and grouting. Cement residue and harsh cleaners can mark the finish.
6. Skipping the hair strainer
Keep the hair strainer in place. It's the easiest way to prevent slow drains.
Get it right first time
Maintenance Depot stocks linear drains in several sizes and finishes, plus the PVC fittings and cement you need for the connection.
Frequently asked questions
Where do most shower leaks start?
Around the drain, usually because the waterproofing membrane was not sealed properly to the drain body.
How level does a linear drain need to be?
It should be dead level along its length, otherwise water collects at one end.
How do I protect the finish during tiling?
Cover the grate with tape or keep it removed until grouting is finished and cleaned.
Buy Bisman Linear Floor Drain 18" x 2 3⁄4" at Maintenance Depot