Installing a Shower Toilet Seat on an Existing Toilet
A Practical UK Guide for Retrofitting an Electric Bidet Seat
A shower toilet seat, also known as an electric bidet seat, Japanese toilet seat or wash and dry toilet seat, can often be installed onto an existing WC without replacing the complete toilet. It is one of the simplest ways to add warm-water washing, improved hygiene and modern bathroom comfort to your current bathroom.
The key to a successful installation is checking three things before you buy: toilet fitment, cold-water access and a safe electrical supply. This guide explains the process step by step.
Before ordering, check these essentials
A shower toilet seat normally needs the following conditions to be suitable for your existing WC.
- Compatible toilet shape
- Cold-water connection
- Safe electrical supply
Measure Your Existing Toilet Before Purchasing
Confirm the seat will physically fit your WC
Before choosing a model, measure your toilet carefully. The most important dimension is the distance from the seat fixing holes to the front edge of the ceramic bowl. You should also check the distance between the fixing holes and the available space between the fixing holes and the cistern or wall behind the toilet.
- Measure from the fixing holes to the front of the bowl.
- Measure the distance between the two fixing holes.
- Check the space between the fixing holes and the cistern or wall.
- Confirm whether the bowl is round, elongated, D-shaped, square or compact.
If the toilet is unusually shaped, very compact, or has a raised rear section, please contact us before ordering.
Measure the toilet before ordering to confirm compatibility.
Important fitment advice
Most standard close-coupled toilets can be checked easily with measurements. Wall-hung toilets and modern designer ceramics may require closer checking, especially if you want a neat installation with discreet water and electrical connections.
Plan the Water and Electrical Connections
Cold-water access
The shower toilet seat is normally connected to the same cold-water supply that feeds the toilet cistern. This is usually done with a supplied T-connector, allowing one water feed to continue to the cistern and the other to supply the bidet seat.
The connection point may be beside the toilet, behind the cistern, inside the cistern area, or sometimes beneath a nearby washbasin if that gives a cleaner route.
Typical cold-water connection near the toilet cistern.
Electrical access
An electric shower toilet seat also requires a safe electrical supply. The socket or connection should be positioned in accordance with UK bathroom electrical requirements and protected appropriately. Electrical work in a bathroom should be carried out by a qualified electrician.
For a more elegant finish, the cable can sometimes be routed discreetly through the wall, behind bathroom furniture or between tiles. Do not use a loose extension lead in the bathroom.
Plan the electrical supply before installation for a cleaner result.
Professional recommendation
A competent plumber should complete or check the water connection. Any bathroom electrical work should be carried out by a qualified electrician. This helps ensure a safe, reliable and visually clean installation.
Remove the Existing Toilet Seat
Prepare the ceramic bowl
Remove the old toilet seat by loosening the existing fixings. Depending on your toilet, the screws may be accessed from above the ceramic or from underneath the bowl.
Once the old seat has been removed, clean the top surface of the ceramic thoroughly. A clean surface helps the mounting plate sit correctly and keeps the installation stable.
Remove the existing seat and clean the ceramic surface.
Unpack the Shower Toilet Seat and Check the Parts
Check everything before fitting
Carefully open the package and confirm that all installation parts are present. A typical shower toilet seat package includes the electric bidet seat, mounting plate, fixing bolts, water hose, T-connector and instruction manual.
Keep the packaging until the installation has been completed and the seat has been tested. This is useful if any adjustment, exchange or product check is required.
Check the product and installation parts before fitting.
Fit the Mounting Plate to the Toilet
Align the seat before tightening
Position the mounting plate over the existing toilet seat fixing holes. Insert the supplied fixings and adjust the plate until it is centred and aligned with the toilet bowl.
Tighten the screws firmly, but do not over-tighten them. Excessive force can damage the ceramic or fixing components.
The mounting plate must be centred and securely fixed.
Slide the Shower Toilet Seat into Position
Lock the seat onto the mounting plate
Slide the shower toilet seat onto the mounting plate until it locks into place. Check that the seat is straight, stable and correctly positioned over the toilet bowl.
If the seat sits too far forward, too far back or slightly off-centre, release it from the mounting plate and adjust the plate position before continuing.
The seat slides onto the mounting plate and locks into place.
Turn Off the Water and Install the T-Connector
Connect to the cistern water supply
Turn off the water valve feeding the toilet cistern. Flush the toilet to release pressure from the water line, then carefully disconnect the existing hose from the cistern inlet.
Fit the supplied T-connector between the water supply and the cistern connection. Make sure the thread size is correct, the connector sits straight and all seals are properly positioned before tightening.
The T-connector splits the cold-water supply between the cistern and bidet seat.
Connect the Water Supply Hose
Connect and check for leaks
Connect the water supply hose to the T-connector and then to the shower toilet seat. Ensure that each connection is straight and securely tightened.
Slowly turn the water supply back on and check carefully for leaks around the valve, T-connector, cistern inlet and seat connection. If any leak appears, turn the water off and re-check the connection before using the product.
Connect the hose carefully and check each joint.
Final water connection to the shower toilet seat.
Connect the Power and Test the Functions
Final safety and function check
Once the water connection has been checked, connect the shower toilet seat to the electrical supply. Follow the manufacturer’s instructions to test the washing function, nozzle movement, water temperature, seat heating, drying and remote-control functions, depending on the model.
Before regular use, confirm that the seat is stable, the water connection is leak-free and the electrical supply is safe.
After installation, test all functions before regular use.
Will a Shower Toilet Seat Fit Every Existing Toilet?
Not always — compatibility should be checked first
Many standard UK toilets are suitable for a shower toilet seat, but fitment is not universal. Some compact, square, raised-back, designer or wall-hung ceramics may not provide enough space for the seat to sit correctly.
If a seat-only model is not suitable, a complete shower toilet set may provide a better result. Complete models are designed as an integrated ceramic and washing system, usually giving a cleaner appearance and more discreet connection options.
- Choose a seat-only model if your existing toilet is compatible and you want a simple upgrade.
- Choose a complete shower toilet if you want the cleanest design, hidden connections or a more premium finish.
- Contact us first if you are planning several bathrooms or are unsure about compatibility.
Frequently Asked Questions
Can I install a shower toilet seat on my existing toilet?
In many cases, yes. A shower toilet seat can often be installed on an existing toilet if the bowl shape, fixing-hole position, available rear space, water connection and electrical supply are suitable.
Does a shower toilet seat need hot water?
Most electric shower toilet seats connect to the cold-water supply and heat the water internally. The exact heating system depends on the model.
Do I need a plumber?
We recommend using a competent plumber, particularly if the water valve, pipework or cistern connection needs to be adjusted.
Do I need an electrician?
If a suitable electrical supply is not already available, any bathroom electrical work should be carried out by a qualified electrician.
Can the water and electrical connections be hidden?
Sometimes. Hidden connections depend on the toilet, bathroom layout and selected model. If a fully concealed finish is important, a complete shower toilet solution may be preferable.
What should I send to check compatibility?
Please send photos of your toilet from the front, side and top. Also include the distance between the fixing holes, the distance from the fixing holes to the front of the bowl, and the distance from the fixing holes to the cistern or wall.
