Replacing Seals and Cartridges in Viking Radiators

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Replacing the seal and cartridge in Viking taps: a complete professional guide

A dripping tap in the bathroom or kitchen is one of the most common household problems we encounter every day in practice. A dripping faucet that drips dozens of liters of water overnight is not just an annoying sound – it is a real loss of money and unnecessary strain on the water supply network. The good news is that in most cases it is a problem that can be solved by yourself, without the need to call a plumber. Viking taps are designed so that maintenance and replacement of internal components is as practical as possible – cartridges and seals are standardized, available and with a little skill they can be replaced by anyone. This article will explain in detail how to do it.

Before the actual procedure, it is important to clarify what type of tap it is. Viking taps are supplied in several construction variants – single-lever taps with ceramic cartridges, double-lever taps with ball or ceramic valves, thermostatic taps with a thermostatic body and shower sets with various internal mechanisms. Each type has different seals, a different cartridge and a slightly different disassembly procedure. If you are not sure what type of tap it is, I recommend reading the related article Single-lever vs. thermostatic Viking tap: which one is suitable for your case, where the differences are explained clearly.

Why the tap starts to leak or drip – causes and diagnosis

Before you reach for the wrench, it is important to correctly identify where and why the tap is dripping. From practice I know that people often confuse different types of leaks, which leads to unnecessary replacement of components that are not damaged.

The most common leak locations are:

Spout (aerator): The tap drips from the spout even when it is closed. The cause is almost always a worn cartridge or valve seat seal.
Around the lever or handle: Water leaks around the control lever. Cause – damaged O-rings on the cartridge body or worn sealing ring under the lever.
Connection of the tap to the sink or elbow under the sink: Leak at the connecting hoses. This is not a cartridge fault – it is a loosening or damage to the connecting seal.
Around the base of the tap: Water leaks from the lower part of the tap body. Cause – damaged seal between the tap body and the mounting surface, or a crack in the tap body (this is a more serious problem).
Shower hose or head: Leak at the hose connections, not in the tap itself.

Correct diagnosis saves time and money. I recommend thoroughly drying the tap with a paper towel before disassembly and then opening and closing it – carefully observe where the first drop appears. You can also help by placing dry paper towels in different places and checking where they are wet.

Tools and materials you will need

Preparation is half the success. Replacing a cartridge or seal is not a demanding operation, but without the right tools you can unnecessarily complicate the work or damage the tap.

Hex keys (Allen keys): The most common sizes are 2, 2.5, 3, 4 and 5 mm. Screws under the lever covers on Viking taps are most often M3 or M4 with an internal hexagonal slot.
Flat screwdriver: For removing decorative cover caps and covers.
Adjustable wrench or cartridge wrench: For pulling out the cartridge or disassembling the cartridge nut. Never use regular pliers without protection – they scratch the chrome surfaces.
Teflon (PTFE tape): For sealing threaded connections during assembly.
Replacement cartridge or set of seals: It is good to know the exact type of tap and the diameter of the cartridge in advance (standard for lever taps is 25, 35 or 40 mm).
Silicone lubricant: For lubricating new O-rings and seals before assembly – it prolongs their life and makes assembly easier.
Catch basin or towel: During disassembly, water will drain from the tap body.
Camera or mobile phone: I recommend taking photos of each step before disassembly – you will appreciate reference photos during assembly.

As for spare parts: cartridges for Viking taps are made in several diameters – the most common standard for lever taps is a 35 mm ceramic cartridge. Before purchase, check whether it is a cartridge with a right or left orientation of the hole, because interchangeable cartridges with a rotated hole (so-called "rotated") can work, but are prone to incorrect installation and bad rotation direction.

Types of seals in Viking taps – what is what

Viking taps use several types of sealing elements. Each serves a different purpose and has a different lifespan.

Ceramic cartridge

This is the heart of every modern lever tap. A ceramic cartridge contains two precisely machined ceramic plates (a disc and a seat) with a tolerance of several thousandths of a millimeter. Water is closed and controlled by rotating or tilting one plate against the other. A ceramic cartridge is much more durable than rubber seals – with normal use it can last 150,000 to 500,000 cycles of opening and closing. It can, however, become clogged with limescale and sand. If the cartridge leaks (the tap drips), it is usually enough to replace the entire cartridge – it is not economically justified to grind the ceramic plates at home.

O-rings (O-rings)

Rubber sealing rings with a round cross-section. They are located on the body of the cartridge (where the cartridge fits into the body of the tap), on the connections of internal tubes, on connecting nuts and on the connection of the spout to the body of the tap. O-rings dry out, harden and crack over the years, which causes water to leak around the cartridge (not through the cartridge). They are cheap – a typical set of O-rings for a tap costs a few euros – and their replacement is simple.

Flat sealing washer (flat washer)

A traditional seal used in older double-lever taps or cheaper valves. A rubber, fiber or silicone washer sits on the valve seat and closes the water flow. If the tap drips from the spout when closed, this washer is worn. Replacement is simple – unscrew the valve stem, replace the washer and reassemble.

Sealing of connection nuts

It is located on 3/8" or 1/2" threaded connections of flexible hoses. Typically it is a rubber or silicone gasket. If the connection between the hose and the faucet (or the hose and the elbow) is leaking, this seal is the cause.

Procedure for replacing a cartridge in a single-lever valve Viking

This is the most common case you will encounter – a leaking faucet from the spout of a sink, kitchen, or bathtub. The procedure is the same for most lever valves regardless of design.

Step 1: Close the water supply

Before any work, it is essential to close the water supply. Ideally, close the shut-off valves directly under the sink or countertop – one for cold and one for hot water. If the shut-off valves are not installed or not working, you will have to close the main water shut-off valve in the apartment. After closing, open the faucet fully to relieve pressure and drain any remaining water from the pipes. I recommend placing a towel or a basin under the faucet.

Step 2: Remove the handle

On top of the lever, find the colored cap (blue = cold side, red = hot) – it covers the screw that holds the lever. Remove the cap with a thin flathead screwdriver or your fingernail. Underneath, you will find an Allen screw, most commonly M3 or M4. Unscrew it and simply pull the lever upward. If the lever is stuck (which can happen after years in a humid bathroom), try gently moving it side to side while pulling upward – never use brute force on the lever, as you might break the plastic adapter or scratch the chrome finish.

Step 3: Remove and disassemble the body cap

After removing the lever, you will see the chrome cap (also called a cap or escutcheon), which covers the cartridge body and the upper nut. This cap is either screwed in (left-hand thread – turns clockwise when viewed from above!) or secured with screws on the sides. Remove it carefully. Some models also have a plastic adapter underneath – remove it as well and remember its orientation.

Step 4: Remove the cartridge

Now you will see the cartridge nut – hexagonal or with holes for a special key. Unscrew the nut (the standard direction is counterclockwise when viewed from above). Set the nut aside. You can now pull the cartridge straight up – if it is stuck, use a cartridge puller (a special tool) or carefully grip the plastic body of the cartridge with pliers with protected jaws. Never pull the ceramic disk at the bottom of the cartridge. Immediately after removal, remember (or take a photo of) the orientation of the cartridge – some cartridges have an offset hole, and if installed incorrectly, the faucet will work in the opposite direction (hot water on the left, cold on the right).

Step 5: Inspect the condition of the cartridge and housing

Look into the opening in the faucet body where the cartridge was seated. Clean any lime deposits with a soft brush and a descaling solution (e.g., vinegar solution). Check the condition of the seating surfaces – if they are scratched or cracked, the problem may be in the faucet body, not just the cartridge.

Step 6: Install the new cartridge

Apply a thin layer of silicone-based lubricant to the O-rings on the new cartridge. Ensure the correct orientation – the red mark or protrusion on the cartridge must align with the groove in the faucet body (usually backward or toward the hot water side). Insert the cartridge evenly, not crooked. Tighten the cartridge nut – just enough, do not over-tighten, as you might crack the cartridge body or the faucet body. Too loose tightening, on the other hand, will cause a leak around the cartridge.

Step 7: Reassembly and test

Reinstall the body cap, then the lever (don’t forget the screw), and the colored cap. Slowly open the shut-off valves – check for any leaks. Open the faucet and check the flow and temperature control function. If the faucet is working properly – congratulations, the cartridge replacement was successful.

Replacing the seal in a two-handle Viking faucet

Two-handle faucets (also known as cross or ball type) operate on an older principle – each handle controls one valve (one for hot, one for cold water). In older models, it is flat rubber seals on the stem, in newer models it is ceramic discs or mini cartridges.

Replacing the rubber seal (classic valve with flat seal)

The procedure is as follows: turn off the water, remove the decorative cap of the handle, unscrew the handle screw, pull out the handle. You will see a hexagonal valve housing – unscrew it with an adjustable wrench (be careful with chrome surfaces – place a hose or tape underneath). Pull out the stem. At the bottom of the stem you will find a rubber or fiber washer secured by a screw – unscrew it, remove the old washer and install a new one of the same thickness and diameter. Reassemble the entire stem, also check the condition of the O-ring on the stem – if it is hardened or cracked, replace it as well.

When replacing the seal, pay attention to the tightening force of the stem – the so-called "seal travel" is adjusted so that when the handle is fully closed, the faucet does not leak, but at the same time you do not have to tighten the stem with excessive force. Over-tightening will shorten the life of the new seal to a minimum.

Ceramic mini cartridges in two-handle Viking faucets

Newer Viking two-handle faucets use small ceramic mini cartridges instead of a classic rubber stem (so-called 1/4 turn valves – the handle only turns 90°). Their replacement is similar to a full cartridge in a single lever faucet, but the diameter is smaller (typically 15–22 mm). The disassembly procedure is the same – remove the handle, unscrew the housing, pull out the mini cartridge, insert a new one in the correct orientation. The main mistake when installing a mini cartridge in two-handle faucets is incorrect orientation – if you turned it 180°, the handle will open in the opposite direction, which is functionally fine, but unusual to operate.

Replacing the seal in a thermostatic Viking faucet

Thermostatic faucets are more complex in construction. The body of a thermostatic faucet contains a thermostatic element (wax or bimetallic sensor), a control valve and a switching valve (e.g. between the bath and the shower). Thermostatic elements are not usually replaced – if the thermostatic faucet stops maintaining the set temperature, the cause may be a worn thermostatic element or a clogged filter.

What is most often replaced in thermostats: O-rings on the thermostatic body, the seal of the switching valve (if the non-switched branch is leaking), the seal of the connecting joints. Disassembly of the thermostatic body is possible, but I recommend you entrust it to a professional unless you have technical experience – incorrect installation may cause the thermostat calibrated for a safe temperature (46–48 °C) to start releasing much hotter water, which poses a risk of scalding, especially for children.

More on choosing the right type of faucet, including thermostatic models, can be found in the article Single lever vs. thermostatic Viking faucet: which is suitable for your case.

Most common mistakes when replacing a cartridge and seal

Over the years of practice I have seen dozens of cases where a DIY repair turned out worse than the original fault. Here are the mistakes to be especially careful about:

Forgetting to turn off the water: It seems obvious, but it happens regularly. The result is a flooded bathroom or kitchen.
Incorrect cartridge orientation: A cartridge inserted rotated by 180° will cause hot water to be on the right and cold on the left. Someone may not even notice it, but it is non-standard and may confuse another repair person.
Over-tightening the cartridge nut: The plastic body of the cartridge or the body of the faucet may crack when tightened too strongly. Tighten only "firmly" – not to the end.
Replacing the wrong size cartridge: A 35 mm cartridge into a 25 mm housing simply does not fit. Always measure the diameter of the housing or take the old cartridge with you to the store.
Not greasing the O-rings: Dry O-rings deform or crack during installation. Always lightly grease them with silicone-based grease (not oil-based products – they swell the rubber and damage it).
Problem attributed to the cartridge, which is elsewhere: If the faucet still drips after replacing the cartridge, the cause is most likely a damaged seat in the body of the faucet or in the connecting hoses.
Using inappropriate tools on chrome surfaces: Standard steel pliers leave scratches on chrome nuts and housings, which are visible and corrode. Use wrenches with silicone inserts or place a hose underneath.

When Replacing the Seal Isn't Enough and You Need to Replace the Entire Faucet

Not every issue can be solved by replacing the cartridge or seal. From practice, I know several situations where it is economically and technically more sensible to replace the entire faucet:

Cracked or corroded body of the faucet: If you see a crack in the zinc castings or noticeable corrosion on the cartridge seating surface, a new cartridge won't ensure a proper seal. The body of the faucet made from die-cast metal corrodes from the inside over the years, and the surface where the ceramic disc sits becomes uneven.
Chroming or other surface finish is significantly damaged: Technically, this is not a reason for replacement, but aesthetically it is. If the faucet is still functional but looks worn out, replacing the cartridge won't solve the overall aesthetic issue.
The faucet is older than 15–20 years: Spare parts may be hard to find, and even if you manage to find a cartridge, other components (hoses, connectors, sealing rings) may fail soon after.
Repeated failure even after replacing the cartridge: If you've replaced the cartridge and the faucet still leaks, the problem lies elsewhere (seat, O-rings in other places, supply). After a second unsuccessful cartridge replacement, it's appropriate to consider purchasing a new faucet.
Unavailability of a replacement cartridge: For some older or non-standard faucets (for example, with an unusual diameter or special coded marking), spare parts are not available on the market. In such cases, replacing the entire faucet is the only realistic option.

If you're considering buying a new faucet, check the offer at atria.sk – Viking faucets. Before purchasing, it's also worth reading the article Dimensions and connection of Viking faucets: what to check before purchase, where you'll find practical information about the spacing of connections, faucet height, and other important parameters.

How to Extend the Lifespan of Cartridges and Seals – Prevention

Proper care can significantly extend the time between cartridge replacements. A ceramic cartridge that would normally last 10 years may crack or lose its seal in 3–4 years in areas with hard water if not properly maintained.

Installation of a water softener or filter: In areas with hard water (over 300 mg CaCO₃/l), a water filter or softener is an investment that pays off many times over in the lifespan of faucets, boilers, and appliances.
Regular descaling of the aerator and spout: Limescale on the aerator and outlet can also get into the faucet. Regular descaling protects the cartridge from clogging.
Do not operate the faucet with excessive force: A ceramic cartridge works perfectly with a light touch. Pulling the lever hard to the end shortens its lifespan. The faucet is closed as soon as the water stops flowing – there's no need to force it.
Regular inspection of connections: Once a year, check the flexible hoses under the faucet to see if they are leaking or mechanically damaged (bent, cracked). I recommend replacing flexible hoses every 10 years as a preventive measure – a cracked hose can cause major damage.

For more information on maintenance and extending the lifespan of Viking faucets, see the separate article Cleaning and maintenance of Viking faucets: how to extend their lifespan.

Practical Examples from Practice

So that we don't remain just in theory, here are a few typical situations from real service cases:

Case 1 – Basin lever faucet, dripping from the outlet: The customer bought the faucet 7 years ago. The water in the area is moderately hard (around 200 mg/l). The faucet started dripping. Disassembly revealed a ceramic cartridge with clogged holes from limescale and fine sand. The cartridge was not mechanically damaged, but the limescale prevented the ceramic from seating properly. After thorough cleaning of the housing and replacing the cartridge with a standard 35 mm unit, the faucet has been functioning well for several more years.

Case 2 – Bathtub lever faucet, leaking around the lever: A classic case of cracked O-rings on the cartridge body. Water was not leaking from the outlet, but dribbling down the side of the faucet – it had found its way between the cartridge body and the faucet housing. Replacing the complete cartridge, including new O-rings, solved the problem. Cost: about 8 € for the new cartridge and 15 minutes of work.

Case 3 – Two-handle faucet in an older bathroom, only the hot side is dripping: A typical case of a worn rubber seal on the hot water stem. Hot water is slightly more aggressive to rubber than cold water. Replacing the flat seal with a new silicone one (better heat resistance) and checking the O-ring on the stem solved the issue. The total material cost was under 2 €.

Case 4 – Shower faucet, constant leakage into the bathtub even when switched to the shower: The cause was a worn seal on the switching valve. The customer assumed it was a cartridge issue – but the cartridge was fine. After identifying the real cause and replacing the switching seal, the problem was resolved. An important example: proper diagnosis before repair.

Frequently Asked Questions (FAQ)

How do I find out what diameter cartridge I need for my Viking faucet?

The most reliable method is to remove the old cartridge and measure its outer diameter with a caliper. Standard diameters for lever faucets are 25 mm, 35 mm, and 40 mm. Alternatively, find the model number on the faucet housing or in the documentation and compare it with the technical parameters of the seller. If you can't find the marking, take the old cartridge with you to the store – it's the most reliable method. For Viking faucets, 35 mm is the most common standard in typical lever faucets.

Can I replace the cartridge with one from a different brand than the original?

Yes, cartridges are largely universal according to diameter and height. The most popular compatible cartridges come from manufacturers Sedal, Kerox, or Hydroplast – these are commonly available and in most cases compatible with Viking and other brands. It's important to maintain the same diameter, the same height, and the same orientation of the inlet holes (right/left or "rotated" variant). Cheap no-name imported cartridges may have a shorter lifespan – investing in a quality cartridge from a trusted manufacturer pays off.

After replacing the cartridge, the faucet still leaks – what should I do?

The first thing: check whether it's dripping from the same place as before the replacement. If it's dripping from the outlet – the new cartridge is likely misaligned, the seating surface in the faucet body is damaged, or the cartridge is not properly tightened. If it's dripping from a different place than before the replacement – the cause was elsewhere and you've only covered it up by replacing the cartridge. Check the O-rings on the connections, the supply hoses, and the cartridge nut. If the problem persists after a thorough inspection, consider whether the faucet body itself is damaged.

How do I know that the seal needs to be replaced preventively, even before the faucet starts dripping?

Preventive replacement makes sense for faucets older than 8–10 years, especially in areas with hard water. Indicators of an approaching end of life for a cartridge: the lever feels more resistant or, conversely, looser than usual; when closing the faucet, you need to pull a bit more than usual; after closing, the faucet still drips for a while (a few seconds – this is normal residual water in the pipe, but if it lasts a minute, there's a problem). I recommend checking the seals on connections during every replacement of a faucet head or nearby faucet – it's just 5 minutes of extra work and can prevent a bigger repair.

Can I use silicone-based lubricant on all seals and O-rings?

Silicone-based lubricant (silicone grease) is suitable for most rubber and ceramic seals in faucets. Do not use oil-based lubricants (WD-40, tool oil, petroleum-based vaseline) – these swell rubber materials and cause rapid wear. On the threads of supply hoses, use PTFE tape (teflon) instead of grease. For certain special O-rings (e.g., made of EPDM or NBR rubber), it's appropriate to use a specific lubricant designed for that material – information is usually found in the faucet or cartridge documentation.

How long does it take to replace a cartridge in a standard lever mixer?

For the first replacement and using this guide, expect to spend 30–60 minutes including preparation and testing. For subsequent replacements (when you know your specific mixer and have the tools ready), it realistically takes 15–20 minutes. The biggest time loss is searching for the right tools and waiting for the correct replacement cartridge. I recommend always having a set of hex keys and silicone vaseline at home – these are the most commonly used tools for any mixer repair.

Conclusion: cartridge replacement as the simplest home installation repair

Replacing a seal or cartridge in a Viking mixer is one of those home repairs where a little courage and preparedness pay off. Everyone can manage it who has the right tools available, knows how to shut off the water supply and is willing to proceed methodically. The material costs are minimal (5–25 € for a new cartridge, cents for seals), while an plumber charges several times more for the same job.

The most important rules to remember: correct diagnosis of the leak location, correct identification and diameter of the cartridge, lubricating O-rings with silicone, correct orientation of the cartridge during installation and appropriate tightening force. If the repair still fails despite this or the mixer is mechanically damaged, consider investing in a new mixer from the Viking mixer range – a quality new mixer with a ceramic cartridge can serve you for another 15–20 years without any intervention, provided you take regular care of it.

For a comprehensive overview of common problems and their solutions, I recommend reading the article Common Viking mixer faults and how to eliminate them, where you will find further diagnostic tips for less typical faults as well. And if you are considering a new installation or replacing the entire mixer, the article Step-by-step installation of a Viking water mixer will provide you with an equally detailed guide through the entire installation process.

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