The shower drain is the system that evacuates water from the shower tray or floor into the downpipe, retaining unpleasant odours with a water seal (trap). There are two main types: the point drain, with a valve or square strainer, and the linear drain or channel. Choosing the right one depends on the flow rate, the available height, and the type of shower tray.
It is the part that is looked at the least and causes the most problems when it fails: a poorly chosen drain causes water to pool, the typical sewer smell to rise, or the tray to clog every few weeks. In this guide, we explain how it works, the different types, what to look for when buying it, and how to maintain it. All technical data is taken from the actual product sheets in the Merkimarket shower drain collection.
Key shower drain specifications
- Two main types: point drain (valve or square strainer) and linear drain or channel.
- Tray hole: the standard for resin and ceramic trays is a hole with a diameter of 90 mm.
- Downpipe outlet: usually 40 mm, horizontal or vertical depending on the installation.
- Evacuation flow rate: it is advisable to look for models that exceed 25–30 L/min; extra-low profile models perform slightly less.
- Profile (height): there are extra-low profile versions designed for floor-level trays with very little height under the slab.
- Water seal: this is the layer of water that blocks odours; it should never be left dry.
- Common materials: chrome-plated brass in valves (TRES), ABS and stainless steel in grates and plates (Roca In-Drain).
- Warranty: minimum legal three-year warranty for consumers in Spain.
Now you have the map; below we develop each point so you can choose without making a mistake.
Point drain or linear strainer: the two main types
The first decision is how to evacuate the water. The point drain is the classic: a valve or square strainer placed in the centre or in a corner of the tray, to which the water reaches thanks to a slight slope. It is the most economical, the easiest to replace, and the one used in most resin trays. In the catalogue, this includes the TRES brass drain valve with a chrome finish, a robust piece designed to last.
The linear drain or channel is the design option: an elongated grate, normally attached to the wall or the shower screen, which allows the floor to have a single slope and achieve that continuous shower effect so sought after in modern bathrooms. It evacuates a lot of water and looks very clean aesthetically, although it requires more construction work and a greater slab height. The Roca In-Drain Plate X2 adaptable 65 cm wide drain grate plate is a good example of this format.
Evacuation flow rate: the figure almost no one looks at
The flow rate is the amount of water the drain is capable of handling per minute, and it is the difference between showering with the water running or having the tray turn into a small pool. A modern showerhead can easily release more than 15 L/min, and a tropical rainfall showerhead much more, so the drain must be more than adequate. As a reference, it is advisable to choose models that comfortably evacuate above 25–30 L/min; the exact figures vary with each model and you will find them in its product sheet.
Be careful with extra-low profile models: they gain height (they are ideal when there is little space under the tray) but usually sacrifice some flow rate, because the water has less vertical distance to gain speed. If your shower is one of the high-flow ones, prioritise a drain that will not fall short over the lowest possible profile.
Why the shower drain smells bad (and how to prevent it)
The sewer smell that sometimes rises through the shower does not come from dirty water: it comes from the air in the downpipe, and what should stop it is the water seal. Every good drain incorporates a small trap —a curve or a bell— that always retains a layer of water. That layer acts as a plug and does not let gases pass.
The problem arises when that seal evaporates, which is typical in showers used occasionally (a second home, a guest bathroom). The solution is as simple as letting the water run for a few seconds every so often to refill the trap. If the smell persists with the seal full, it is most likely that the drain does not have an integrated trap or is poorly sealed against the tray: in that case, the part to check is the gasket.
For odour problems in other areas of the bathroom, our guide on sink traps, bad odours and leaks may be useful.
Clogs: why they occur and how to prevent them
The number one enemy of the shower drain is hair, which gets tangled and, mixed with soap residue, gel, and limescale, forms clogs that gradually reduce the flow rate. It is usually not a sudden clog, but an increasingly slow evacuation until one day the water does not go down. Preventing it is much easier than solving it:
- Place a filter or hair-catching grate over the hole and empty it every week.
- Avoid flushing solid residues down the shower and try not to use thick body oils excessively.
- Once a month, let very hot water run to dissolve the accumulated grease.
- Check that the cap or valve can be removed without tools to clean it inside.
Many current drains, such as the models with a removable cap like Roca Aqua, incorporate that piece precisely to be able to access the interior and remove hair easily.
Measurements and compatibility: diameter, height, and tray
Before buying, you need to look at three measurements. The first is the diameter of the tray hole: the standard for resin and ceramic trays is 90 mm, but it is advisable to confirm it because there are exceptions. The second is the downpipe outlet, normally 40 mm, and whether it is horizontal or vertical depending on how the drain in your home is set up. The third is the total height of the piece, which must fit in the space left under the tray.
This table summarizes the two main options so you can see at a glance which one fits best in your renovation:
| Type | Flow rate | Aesthetics | Installation | Ideal for |
|---|---|---|---|---|
| Valve / point drain | Medium-high | Discreet, centred or in a corner | Simple, direct replacement | Resin trays and quick renovations |
| Extra-low profile drain | Medium | Almost invisible | Little space under the tray | Floor-level trays with little height |
| Linear drain / channel | High | Design grate | More construction work, higher slab | Built-in showers and continuous flooring |
How to clean and unclog the drain step by step
If the water is already draining slowly, there is no need to call the plumber right away. Follow these steps before resorting to anything more aggressive:
- Remove the grate or cap. Most are removed by hand or by turning a quarter turn; do not force with a screwdriver if it is not necessary.
- Remove visible hair. With pliers, a hook, or a hair-catching brush, remove the hair and soap plug that is almost always right under the grate.
- Clean the trap basket or cup. If the model allows it, unscrew the inner part and wash it with hot water and a brush.
- Flush out the grease. Pour very hot water (not boiling over resin) to dissolve the soap and gel residues left on the walls.
- Try baking soda and vinegar. A glass of baking soda followed by vinegar, letting it work for 15 minutes and rinsing, solves most minor clogs without damaging the pipe.
- Reassemble, checking the gasket. When replacing the valve, make sure the rubber sits well against the tray to prevent leaks and odours.
Avoid strong chemical drain cleaners habitually: they solve the problem in the short term but dry out gaskets and rubbers, and eventually cause leaks. If after cleaning the drain the water still does not go down, the clog may be further down, in the downpipe, and then it is advisable to resort to a plunger, a cable, or professional help.
How to choose your shower drain in 4 steps
- Measure your tray. Hole diameter (normally 90 mm) and available height under the tray. This is what rules out or validates each model.
- Decide point or linear. For a simple replacement, a valve; if you are renovating from scratch and looking for design, a channel.
- Prioritise the flow rate. Especially if you have a rainfall shower or large showerhead, choose a drain that evacuates with plenty of capacity.
- Check the access for cleaning. Having the cap or grate removed without tools will save you many future clogs.
Ready to choose? Explore the entire collection of shower drains at Merkimarket, with models from Roca, TRES and Unisan and shipping throughout Spain. And if you are in the middle of a renovation, our guide on how to choose the shower tray will help you.
Frequently asked questions about shower drains
What diameter does a shower tray drain have?
The standard hole for resin and ceramic trays is 90 mm in diameter, while the outlet to the downpipe is usually 40 mm. It is advisable to confirm both measurements in the tray product sheet before buying the drain.
Why does my shower drain smell bad?
Almost always because the water seal (the layer of water in the trap) has evaporated and lets the air from the downpipe through. Letting the water run for a few seconds to refill the trap is usually enough; if it persists, check that the drain has a trap and that the gasket with the tray is well sealed.
How do I unclog the shower drain without chemical products?
Remove the grate and the accumulated hair with pliers, clean the trap basket with hot water and use baking soda with vinegar, letting it work for 15 minutes. It is effective for minor clogs and does not damage gaskets or pipes.
Which is better, a point drain or a channel?
It depends on the renovation. The point drain is cheaper and easy to replace, ideal for resin trays. The channel or linear drain evacuates more water and looks more aesthetic, but requires more construction work and a higher slab.
Article written by the Merkimarket editorial team. Technical data (measurements, materials and drain types) taken from the product sheets in the Merkimarket shower drain collection. Measurements and availability may vary; consult each product sheet for the information current in Spain.
