Direct answer: Most of the time, rats are not coming through the shower drain itself. They are using an open gap around the shower drain pipe, trap arm, or a larger wall or floor chase nearby, then surfacing at the drain opening or trim area.
Most likely: The most likely cause is a poorly sealed pipe penetration around the shower drain line or an access opening left open after past plumbing work.
Start by figuring out exactly where the animal path is. A rat at a shower drain can mean a simple open penetration around the pipe, but it can also point to a larger hidden opening under the pan or a damaged drain or vent path. Reality check: if a rat can show up there, the opening is usually bigger than it first looks. Common wrong move: sealing the visible edge at the shower floor while leaving the bigger chase open below.
Don’t start with: Do not start by packing the opening with foam alone or by buying drain parts before you know whether the gap is around the pipe, inside the drain body, or tied to a broken drain line.
You see movement at the shower drain grate or hear scratching directly below it, especially at night.
Start here: Start by removing the drain cover and checking whether the path is inside the drain body or around the outside of the drain pipe below the shower floor.
From the ceiling below, crawlspace, or tub access opening, you can see daylight or a rough oversized hole around the shower drain pipe or trap arm.
Start here: Start below the shower if you can. A visible penetration gap is more likely than a rat squeezing through a water-filled trap.
You find droppings, shredded insulation, or a musky odor around the shower wall, vanity side, or ceiling below.
Start here: Look for a larger wall or floor chase near the drain line, vent line, or supply penetrations before focusing only on the drain opening.
The shower drains fine, there is no backup, but rats are still surfacing near the drain area.
Start here: That usually points to an entry gap around the plumbing, not a clog. Inspect the pipe path and surrounding framing openings first.
Plumbers and tile crews often leave an oversized cutout around the drain pipe or trap area, especially where the pipe passes through subfloor or framing.
Quick check: Use a flashlight from above and below if possible. Look for a rough annular gap, missing patch material, or visible insulation and framing around the pipe.
Rats usually use the biggest hidden opening available, then show up at the drain because that is where the cavity meets the shower base.
Quick check: Check nearby access panels, vanity backs, ceiling openings below, and corners where multiple pipes run together.
If the trap, trap arm, or nearby drain line is damaged or disconnected, the opening can be large enough for pests and may also bring sewer odor or moisture.
Quick check: Look for staining, damp framing, sewer smell, loose piping, or a drain that shifts when touched from below.
A missing grate or loose drain assembly does not create the whole route by itself, but it can leave the final opening exposed once rats reach the cavity below.
Quick check: See whether the drain cover is missing, broken, or loose and whether the drain body has obvious movement or broken edges.
You need to separate a true drain-path problem from a simple pipe-gap problem before you seal anything.
Next move: You find the actual route, whether it is around the pipe, through a larger framing opening, or tied to damaged drain piping. If you cannot see the pipe path from above and there is no access below, you may need a plumber or pest pro to open the least-destructive access point.
What to conclude: Most homeowners find the problem is around the drain line, not through the trap water itself.
An open or damaged drain line changes the job from simple exclusion to plumbing repair first.
Next move: If the drain holds water, drains normally, and stays dry below, you can focus on sealing the entry gap. If you find leakage, sewer odor from an open line, or a loose broken drain assembly, repair the plumbing opening before any exclusion work.
What to conclude: A dry, normal-draining shower usually means the rat route is beside the plumbing, not through a failed drain path. A wet or smelly cavity points to damaged drain piping or a failed shower drain connection.
Once the plumbing is sound, blocking the real route is what stops repeat entry.
Next move: The route is physically blocked at the cavity opening, which is what usually stops the problem for good. If you cannot create a solid closure because the opening is too large, wet, crumbling, or tied into hidden damage, bring in a plumber or qualified repair contractor.
Drain parts help only when they are actually broken, missing, or loose.
Next move: You restore a sound drain path and remove any opening created by broken plumbing parts. If the damaged section is buried in the shower base, slab, or finished ceiling with no clean access, this is plumber territory.
A good repair should stop the route, but you want to confirm there is no second opening nearby.
A good result: No new droppings, noise, or sightings show up, and the shower drains normally with no leaks.
If not: If rats keep appearing, there is still another opening in the same cavity or a larger building-entry problem outside the bathroom.
What to conclude: When the shower area stays quiet after sealing and normal use, you likely closed the real route.
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Usually not through a normal water-filled trap by itself. More often they are using an open gap around the shower drain pipe, a nearby wall chase, or damaged drain piping and then surfacing at the drain area.
No. It will not fix the entry route, and it can create a chemical hazard. Find and close the actual opening instead.
Not by itself. Foam alone is a common failure. It may hide the gap for a while, but rodents can chew through it. The repair needs a solid, rodent-resistant closure at the real opening.
That usually means the plumbing is working and the problem is an access gap around the pipe or in the surrounding cavity. Focus on inspection below or beside the shower, not on clog clearing.
Call a plumber if you find a leaking or broken shower drain body, cracked trap or drain pipe, sewer odor from an open line, or if the repair requires opening the shower base, tile, or a finished ceiling.
If this was a one-opening problem and you sealed it well, maybe not. If you have repeat sightings, droppings in more than one area, or noise in several walls, you likely need both exclusion work and pest control.