8 tips for good drainage in bathrooms with walk-in shower

TIP 1: sufficient flow capacity

Ensure you have a shower drain with sufficient flow capacity. Carrodrain is a good choice for that with 31 litres per minute. The flow of a modern showerhead can vary enormously. From a water-saving version with 5 litres per minute up to 25 litres of water per minute. You shower drain will therefore have enough drainage capacity. If dirt or hair temporarily lower the drainage flow, the water still needs to be easily drained.


TIP 2: correct slope of the drainage pipe

It seems like it would make sense to place the drainage at as steep a slope as possible. This is not always the best method, however. If a horizontal drainage pipe is on too steep a slope, dirt remnants may dry in the drainage pipe and cling to the inside of the pipe. On the other hand, if the pipe does not drain enough, the water will stay in it and the sediment can also get stuck in the pipe. These contaminations can then block new deposits that will further block the pipe. The result is a completely blocked pipe. The ideal slope of a horizontal drainage pipe is 1 cm per metre. This does not apply to the vertical main drainage; this may be run straight down.


TIP 3: correct diameter of the drainage pipes

To ensure a smooth flow, it is essential to install pipes with the correct diameter. This diameter depends on the expected flow capacity. These are some minimum diameters (bigger is allowed

    • Lavabo: 40 mm, never drain together with the bathtub
    • Walk-in shower with shower drain: 50 mm, with the reduction part supplied by Carrodrain, you can immediately link to a 50mm pipe. Always drain separately to the main drainage pipe/rising main
    • Bathtub: 50 mm, always drain separately to the main drainage pipe/ rising main
    • Washing machine: 40 mm, always drain separately to the main drainage pipe / rising main
    • Dishwasher: 40 mm, always drain separately to the main drainage pipe / rising main
    • Toilet: 90 mm, always drain separately to the main drainage pipe / rising main

If different drainage pipe come together, choose a diameter as big as possible, such as 110 mm. Always ensure that the water does not have to travel too much distance horizontally through a pipe of limited diameter. If it does have to travel a bigger distance horizontally, switch to a bigger diameter a soon as possible to prevent blockages.

The same is true for bringing together the drainage of multiple appliances. If circumstances do not allow you to drain the appliances separately, ensure that you have enough of a margin in the diameter of your drainage pipe. If the vertical main drainage pipe is of insufficient diameter, this may create a vacuum effect. This could cause the siphons of the shower drain and the other bathroom appliances to be emptied, which may cause odour nuisance.


TIP 4: avoid air bubbles in the drainage pipe

Air bubbles form when water is being drained and sometimes get stuck in unexpected places. An air bubble that stays in the pipe can slow down or even block the smooth drainage flow. Air bubble formation happens where a horizontal drainage pipe is connected to a vertical pipe using a Y-coupling. Instinctively, you would expect that this would be good for a smooth drainage flow, but because of this Y-coupling (45°), an air bubble may get trapped between the vertical drainage pipe and the shower drain, which may hinder the drainage. The water will then stay in the shower until the siphon is taken out of the drain. Bubbles will form on this, which will escape from the drainage pipe and then the water will suddenly drain very fast. This phenomenon can be avoided by linking to the vertical drainage pipe with a T- coupling. This will prevent the extra air from getting trapped in the horizontal pipe, and it will get removed to the vertical drain.


TIP 5: watch for the double siphon

This tip goes with the previous one. Sometimes, a second siphon forms further down the drainage pipe, intentionally or unintentionally. This will automatically cause an air bubble to get stuck between the two siphons. It is difficult for the water to get past this air bubble, so that the water will no longer drain. If there is an actual second siphon in the drainage pipe, this flaw can easily be side-stepped. The second siphon also hold back the odour, so you can remove the siphon in your shower drain. If there is still an odour it means that no second siphon has been formed and the cause must be found elsewhere.


TIP 6: separate drainage for each appliance

Always try to provide separate drainage for each appliance in your bathroom. Always keep the bathroom and the shower drain separate from each other and from the other bathroom appliances. When you drain the bathtub, this creates a lot of pressure in your drainage pipe, especially if the diameter is not very big. Due to this vacuum effect, the drainage water will then empty the siphons of the other appliances. This may also cause unpleasant odours. If several appliances are connected to a central drainage with a limited diameter or insufficient aeration, this may create a vacuum effect, which will empty the siphons of the shower drain and other appliances. Fortunately, there is a solution to this flaw. You can install a so-called ‘sniffer’ or air intake on the drainage pipe on your toilets or in the pipe shaft. This is a kind of valve that takes in air as soon as there is too much pressure in your drainage pipes. This will allow you to keep the water lock on your other appliances intact. Also see TIP 8.


TIP 7: easily accessible siphon

If your water drainage suddenly slows down, there may be dirt in the siphon of your shower drain. It is therefore very important that the siphon of your walk-in shower be easily accessible and cleanable. You should definitely avoid shower drains and shower trays in which the siphon is inaccessible and installed underground (swan-neck siphon). In the event of a blockage, you will have to break out the entire shower floor, with all the consequences of this. All Carrodrain shower drains have an easy-to-clean and removable siphon. If the water in your walk-in shower no longer drains smoothly, you can simply remove the siphon and clean it. If several appliances are not draining properly at the same time, the problem is probably further down the drain. Perhaps a pipe is clogged or perhaps the septic tank needs to be emptied.


TIP 8: ensure good aeration

This tip spans several of the previous items. If the vertical drainage pipe is properly "aerated," then you are already going to avoid many of the above problems. A good aeration is in fact nothing more than a supply of air to the drainage pipe so that it cannot create a vacuum. This vacuum effect will cause the water to stay in the drain tube. Think of a pipette or a straw that you close off at the top with your finger. The liquid stays in despite the opening at the bottom. There are several ways to aerate a drainage pipe but ideally, the main drain runs vertically through the roof as a 'relaxation pipe' so that it can always take in fresh air. Because the aeration is done on the roof there is never any odour nuisance.

Make sure that the central drainage pipes remain accessible at all times. If, due to circumstances, a central ventilation is no longer possible, the only solution is to provide an aerator on the sanitary appliances already installed. See also TIP 6.