Modular Linear Shower Drain Hair Filter — flushable, 3-layer, parametric

Linear shower drain hair filter — modular, flushable, parametric

A drop-in insert that sits inside a linear shower drain, underneath the stainless grate. It catches hair before it reaches the trap, and unlike a flat filter sheet it can be flushed clean without taking anything apart.

The stainless grate stays where it is and keeps carrying your weight. This part does the filtering, out of sight, in the 18 mm of channel depth underneath.

Why three layers

A single mesh sheet is a sieve: any hole big enough to pass water is big enough to pass a hair. Two stacked layers only close the gaps if the ribs are at least as wide as the holes, which forces the holes small and clogs quickly.

Three layers, each shifted a third of a pitch, close every straight drop with ribs only a third of the pitch wide. That means 2.8 mm holes and still no straight path from the shower floor to the trap.

Verified on the exported mesh, not assumed from the parameters — the generator ray-traces every file it writes:

verticaal          100.00% blocked   (12 000 vertical rays)
20 degrees off     100.00% blocked
40 degrees off      95.40% blocked
plenum 1 clear      5 of 9 channels end to end
plenum 2 clear      9 of 9 channels end to end

Flushing instead of scrubbing

Between the layers sit two 3.4 mm plenums — the space where hair actually gets stuck on multi-layer filters, and normally the space you can never reach. Both plenums open into:

• flush ports in each end wall,

• vents in both side walls,

• notches through the internal ribs, so a plenum is one connected volume rather than a row of dead-end channels.

Point a shower head at the end and the trapped hair comes out the side. If a plug is stubborn, 1.75 mm filament or a piece of wire pushes straight through.

Fits without measuring your channel to the tenth

The body is 45 mm wide with springy 0.8 mm skirts angled outward, giving 61 mm over the tips. They flex on the way in and seal against the channel wall, which also closes the gap along the edge where hair otherwise slips past. Works in roughly a 46–61 mm opening.

Modular

Segments butt end to end with two loose dowels per seam. Nothing sticks out of the bounding box, so the printable length is your bed length. Print as many as your channel needs — four 197 mm segments make 788 mm.

What's in the download

Different drain? Regenerate it

python3 goot_v18_generator.py <length> <width> <height> <pitch> <rib>
python3 goot_v18_generator.py 197 45 18 4.4 1.6      # the file above
python3 goot_v18_generator.py 160 52 16 4.0 1.4      # shorter, wider, finer

Needs trimesh, manifold3d, shapely. The script validates the parameters, refuses combinations that would leave straight drops open, ray-traces the result and fails rather than exporting a mesh that isn't watertight — which it does catch: some lengths produce a bad boolean, so if a run fails, move the length by 5–10 mm.

Printing

• Orientation: mesh face down on the bed — rotate 180° about X. This is the one thing that matters. Printed the other way up, the bottom mesh layer would have to bridge the whole 42 mm chamber.

• PETG. 0.4 mm nozzle, 0.2 mm layer, 4 perimeters, no supports, no brim needed.

• Turn thin wall detection and ironing off. Both will smear the 2.8 mm holes shut.

• Every wall is a whole number of 0.4 mm extrusions and every height a whole number of 0.2 mm layers: ribs 1.6 (4 lines), side walls 1.6, end walls 3.2, mesh layers 1.2 mm (6 layers), plenums 3.4 mm (17 layers).

• Sanity check in the preview: the first layer should be a grid of open squares across almost the whole footprint. A solid area or a bare outline means it's upside down.

Fitting

1. Print the 55 mm coupon.

2. Lift the grate, drop the coupon in, put the grate back. It has to sit flat — the nibs on the underside of most grates take a few millimetres.

3. If it sits proud, regenerate with a lower height. If the skirts don't touch the walls, raise SKIRT_OUT.

4. Only then print the full run.

Cleaning

Lift the grate, lift the segments, rinse from above. Once every few months push the shower head against an end wall and flush the plenums sideways.

Honest limits

• The flow figures are calculated, not measured. The generator prints an "effective open area" using an assumed 0.45 factor for the tortuous path through three layers. That factor is an engineering guess. The geometry numbers (open area, hole size, chamber cross-section, blocked-ray percentage) are measured off the mesh and are real; anything in litres per minute is a calculation.

• Untested in the sense that matters most: this design has not yet run for a season in a real shower. Long-term soap loading is the unknown.

• It is a filter, not a floor. Do not stand on it with the grate removed — the ribs are 1.6 mm.

• The failure mode is deliberate: when it loads up, water stands visibly in the channel long before anything overflows. There is no bypass, because a bypass is an unfiltered route to the trap.

Licence

See post