Can an electric towel warmer be installed directly above a bathtub? Prohibitions to be aware of.

Why are water and electricity incompatible above a bathtub?

Before addressing the technical rules, it's important to understand why installing an electric towel warmer above a bathtub presents a real, not just theoretical, danger.

The mechanism of electrocution in the bathroom

A person in a filled bathtub is in a situation of maximum electrical vulnerability for three combined reasons. Firstly, their body is immersed in water, which conducts electricity. Secondly, their wet skin has an electrical resistance up to 50 times lower than dry skin. Thirdly, lying in water makes any protective reaction almost impossible in the event of an electric shock.

Under these conditions, a current of only a few milliamperes can cause muscle tetany, ventricular fibrillation, or cardiac arrest. The 230V voltage of the household grid is more than sufficient to create this deadly current through bathwater.

Possible accident scenarios

A towel warmer installed above a bathtub can cause electrocution in several ways:

• Appliance falling into the bathtub due to faulty mounting
• Water splashing onto the appliance, penetrating the casing, and causing a short circuit
• Direct contact of a person in the bath with a live part of the appliance
• Electrical arc in case of internal appliance failure in the presence of excessive humidity

Volume 1: The strictly prohibited zone

Volume 1 is the zone defined by the NF C 15-100 standard that directly surrounds the bathtub above the top edge level. This is where the question of installing the towel warmer "just above" the bathtub arises.

Precise definition of Volume 1

Volume 1 extends:

• Vertically: from the top edge of the bathtub to the ceiling (or up to 2.25 m in height if the ceiling is higher)
• Horizontally: within the limits of the vertical projection of the external outline of the bathtub—meaning exactly above the surface occupied by the bathtub

In short: all the space directly above the bathtub, from its top edge to the ceiling, is in Volume 1.

What is strictly prohibited in Volume 1

In Volume 1, no 230V electrical appliance is allowed, regardless of its IP certification. The only permitted equipment are:

• Appliances powered by safety extra-low voltage (SELV, 12V maximum) with a transformer installed outside the zone
• Lighting fixtures specifically certified for Volume 1 (minimum IP45, SELV)
• Electric water heaters specifically designed and certified for this volume

A standard 230V electric towel warmer, regardless of its IP rating (even IP68), can never be installed in Volume 1. This prohibition is absolute and without possible derogation.

Volume 2: Allowed under strict conditions

Volume 2 is the zone adjacent to Volume 1, extending 60 cm around the bathtub. It is in this volume that a conditional towel warmer installation is possible.

Precise definition of Volume 2

Volume 2 extends:

• Horizontally: from 0 to 60 cm beyond the outer edge of the bathtub (horizontal measurement)
• Vertically: from the floor up to 2.25 m in height
• Outside the limits of Volume 1 (therefore not above the bathtub, but next to it)

In practice: the wall against which the bathtub is placed, within 60 cm around it, is in Volume 2. The wall at the head or foot of the bathtub, if the horizontal distance from the outer edge is less than 60 cm, is also in Volume 2.

What is allowed in Volume 2

In Volume 2, a 230V electric towel warmer can be installed on the strict condition that it has a minimum IP44 protection rating (some electricians and some versions of the standard recommend IP44 rather than IP24 for this volume in the presence of a bathtub, due to the risk of significant splashing during baths).

The electrical supply must also be protected by a 30mA differential, and the connection must be made by a qualified electrician with a fixed, recessed supply—no mains sockets are allowed in Volume 2.

Volume 3: The safe zone

Volume 3 is all the space in the bathroom located beyond Volume 2, i.e., more than 60 cm horizontally from any water point. This is the preferred zone for installing a standard electric towel warmer.

Definition of Volume 3

Volume 3 includes all the space in the bathroom that does not belong to Volume 0, Volume 1, or Volume 2. In practice, this is the space located more than 60 cm horizontally from the bathtub, shower, and sink—which, in a normal-sized bathroom, usually represents the wall opposite the bathtub and part of the side walls.

What is allowed in Volume 3

In Volume 3, a standard 230V electric towel warmer (minimum IP20) can be installed without particular IP rating restrictions. However, general rules apply:

• Dedicated electrical circuit from the distribution board (16A circuit breaker)
• Mandatory 30mA differential protection for all bathroom circuits
• Fixed power supply connected by a qualified electrician
• Compliance with wall mounting rules adapted to the appliance's weight

How to measure volumes concretely

The theory of volumes is clear, but its practical application in your bathroom may require some clarification.

Necessary tools

A simple tape measure is sufficient to determine which volume your installation location is in. You do not need specialized equipment or to call a professional for this measurement.

Step-by-step measurement method

Step 1: Identify the outer edge of your bathtub (the most protruding part towards the room, usually the long side of the bathtub).

Step 2: Place your tape measure horizontally from this outer edge to the intended location for your towel warmer.

Step 3: Read the distance. Less than 60 cm = Volume 2, more than 60 cm = Volume 3.

Step 4: Also check the vertical position. If the intended location is directly above the bathtub's surface (in its vertical projection), you are in Volume 1 regardless of height—installation is prohibited.

Ambiguous cases

The most ambiguous case is that of the wall at the head of the bathtub (the short side). If the bathtub measures 170 cm and your bathroom is 200 cm long, the wall at the head of the bathtub is only 30 cm from the edge of the bathtub—clearly in Volume 2. If the bathroom is 250 cm, the distance is 80 cm—in Volume 3. Always measure.

Special case: Bathtub with a screen or shower cabin

The presence of a shower screen or cabin around the bathtub significantly modifies the volume rules and can allow installations that would be prohibited without this protection.

The shower screen: how it modifies volumes

When a bathtub is equipped with a fixed and watertight shower screen at least 2.25 m high, the area above the bathtub is no longer considered an open space subject to water splashes. In this case, the volumes are redefined, taking the screen as the new limit.

In practice: if a 2.25 m watertight glass screen separates the bathtub from the rest of the bathroom, the wall outside the screen can be considered outside Volume 1, and Volume 2 distances are calculated from the screen itself rather than from the edge of the bathtub.

Conditions for the screen to modify volumes

For the presence of a screen to allow the redefinition of volumes, several conditions must be met:

• The screen must be fixed and permanent (not a shower curtain)
• It must reach a height of at least 2.25 m
• It must be watertight against water splashes in all directions
• It must be solidly fixed to the wall and floor without gaps through which water could escape laterally

A shower curtain, even a thick one, does not meet any of these conditions and does not modify the regulatory volumes. Only a properly installed rigid partition can be taken into account.

The case of the shower cabin integrated into the bathtub

Fully enclosed bath-shower cabins (sliding or hinged doors on three or four sides) are the most favorable configurations. In these installations, the space outside the cabin is considered outside Volume 1 as long as the cabin is properly sealed, and Volume 2 distances are calculated from the outer walls of the cabin.

The most frequent scenarios and how they are handled

To concretely illustrate the application of volume rules, here are the most frequently encountered configurations.

Scenario 1: Small bathroom, bathtub against the back wall

In a 1.80 m × 2.20 m bathroom with a 1.70 m bathtub placed against the back wall, the front wall is about 10-20 cm from the edge of the bathtub. This wall is entirely in Volume 2. An IP44 towel dryer is necessary for any installation on this wall.

Scenario 2: Medium bathroom, bathtub against a side wall

In a 2.20 m × 3.00 m bathroom with a 1.70 m bathtub placed against the side wall, the wall facing the bathtub is more than 60 cm from the outer edge of the bathtub (depending on the width of the bathroom). This wall can be in Volume 3. A standard IP20 towel dryer is sufficient on this wall.

Scenario 3: Large bathroom, island bathtub

An island bathtub (not against a wall) creates a Volume 1 zone directly above the bathtub and a Volume 2 zone within a 60 cm radius around it. The bathroom walls, if sufficiently far from the island bathtub (more than 60 cm), are in Volume 3. Standard installation is allowed on these walls.

Scenario 4: Bathtub recessed in a niche

A bathtub recessed in a niche with three walls (back and two sides) creates Volume 1 zones on the three walls of the niche and in the space above the bathtub. The wall outside the niche (facing the bathtub) is generally in Volume 3 if the bathroom is large enough. No installation is possible on the walls of the niche (Volumes 1 and 2).

Alternatives if the desired location is prohibited

If your bathroom configuration does not allow you to install the towel dryer in the initially desired location, here are the alternatives to consider.

Alternative 1: The wall facing the bathtub

In the vast majority of bathrooms, the wall facing the bathtub is more than 60 cm from the edge of the bathtub — therefore in Volume 3. This is the most natural and frequent substitute location. The disadvantage is that towels are less immediately accessible when getting out of the bath, but safety takes precedence over practicality.

Alternative 2: The bathroom entrance wall

The wall on which the bathroom door opens is often the furthest from all water points — and therefore the safest for electrical installation. A towel dryer installed on this wall is generally in Volume 3, regardless of the size of the bathroom.

Alternative 3: Install a shower screen to modify the volumes

If you are renovating your bathroom and absolutely want to install the towel dryer near the bathtub, consider installing a fixed 2.25 m shower screen around the bathtub. This screen modifies the regulatory volumes and can allow for a towel dryer installation that would otherwise be prohibited. The cost of a fixed shower screen (€300 to €800) may be justified by the room's configuration.

Alternative 4: The freestanding towel dryer without wall installation

For bathroom configurations where no wall is available in Volume 3, a freestanding or floor-standing towel dryer is a fallback solution. These devices plug into a power outlet in Volume 3 (more than 60 cm from the bathtub) and can be positioned anywhere you want in the room, without work or fixed installation.

The real risks of non-compliant installation

To conclude, it is important to concretely assess the consequences of non-compliant installation, beyond the immediate electrical risk.

Risk to individuals

This is obviously the most serious risk. A towel dryer installed in Volume 1 or Volume 2 without a sufficient IP rating creates a real and permanent danger for all people using the bathtub. The probability of an accident may seem low on a daily basis, but it is real — and its consequences potentially fatal.

Insurance risk

In the event of an electrical incident (fire, electrocution) in your bathroom, the insurer will appoint an expert to determine the causes. An installation that does not comply with the volumes of the NF C 15-100 standard constitutes a serious fault that can lead to the total refusal to cover the claim. The financial consequences can be considerable, especially in the event of a fire spreading to the rest of the dwelling.

Risk during real estate sale

The mandatory electrical diagnostic for homes older than 15 years includes checking bathroom installations. An identified non-compliance can block the sale, require compliance work, or significantly reduce the selling price.

Criminal liability in rental

For a landlord, a non-compliant electrical installation in the bathroom that causes an accident engages their criminal liability for endangering the lives of others. This liability is particularly heavy if the landlord was aware of the non-compliance without remedying it.