Step-by-step installation of Alveus sink - under-counter, replacement, and built-in installation

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Installation of Alveus sink step by step – undermount, replacement and drop-in installation

Installing a kitchen sink may seem simple at first glance, but in practice, it is precisely during the implementation that most people make a mistake – whether in measuring the cutout, sealing, installing the trap, or connecting to the water supply. I have seen hundreds of Alveus sinks installed across various types of kitchen setups – from cheap laminated worktops to solid stone worktops. Each type of installation has its own specifics. In this article, I will look at all three main installation methods: undermount, drop-in (topmount) and replacing an old sink with a new one. You will find exact dimensions, procedures, practical tips from the field and answers to the most frequently asked questions.

If you have not yet selected a specific model, I recommend reading the articles How to choose the right Alveus kitchen sink – material, shape and size and What sink size do you need – how to measure the cabinet and choose the right dimensions, where you will find a detailed guide on how to proceed even before purchasing.

Basic differences between installation types

Before you start any work, it is essential to know what type of installation you are dealing with. These three variants differ not only in the procedure, but also in the requirements for tools, sealing materials and the demands on the worktop.

Drop-in sink (topmount / drop-in)

This is the most common method of installation in Slovak households. The sink has a rim (flange) around its perimeter that covers the edge of the cutout in the worktop. It is installed from above – simply inserted into the cutout and secured with clips from below. The advantage is simple installation and relatively forgiving accuracy of the cutout. The disadvantage is that the rim collects dirt and during regular cleaning, it is a place where limescale and dirt accumulate.

Undermount installation (undermount)

The sink is attached to the underside of the worktop and the edge of the cutout remains without a rim – the surface of the worktop smoothly transitions into the cutout. This method is much cleaner in terms of aesthetics and easier to maintain. It requires a more substantial worktop (stone, laminated board of at least 38 mm thickness, compact laminate or water-resistant chipboard), because the joints must support the weight of the sink without support from above. Undermount installation is common with stainless steel sinks, while with granite it must be carefully considered, as a granite sink can weigh up to 10–18 kg.

Replacement installation (sink replacement)

When replacing an old sink with a new one, you work in a limited space, without the possibility of freely shaping the cutout. It is crucial that the new sink has the same or larger outer dimensions of the rim (for topmount) or the same cutout dimensions (for undermount). This is in practice the most demanding scenario, because you are working with an existing water and drain installation, sometimes in a confined space.

Tools and materials you will need

Good preparation saves time and nerves. This is a complete list of what you should have ready before starting any installation:

Electric straight line saw (jigsaw) – for cutting the worktop, with a blade for laminate or wood (fine tooth, min. 14 teeth/cm)
Drill and drill bits – for pre-drilling the corners of the cutout (8–12 mm bits) and installing the mounting plate
Kitchen silicone – transparent or white, neutral (acetic silicone can damage some surfaces), at least one 280 ml cartridge
Silicone gun
Adjustable wrench or set of wrenches – for tightening clips and trap
Mounting compound or rubber gasket (supplied with the sink)
Edge tape for cutting laminate
Degreaser and cleaning cloth
Water level
Pencil, measuring tape
Silicon or Teflon tape for trap threads
Bucket and rags – when replacing a sink, there is always residual water in the drain pipe

In some models, such as the ATROX 50 black 91 + pop up trap, the trap is part of the delivery, which significantly simplifies the whole process – you do not have to worry about the compatibility of the drain and trap separately.

Measuring and preparing the cutout – the most important step

Most problems with sink installation arise precisely here. An incorrect measurement of the cutout is one of the things where the mistake is very difficult to correct – it is possible to enlarge the cutout, but it is not possible to reduce it without replacing the entire worktop. Therefore, always measure twice, cut once.

How to measure the cutout for a topmount sink

Each Alveus sink has two key dimensions listed in the documentation (or on the box): the total outer dimension of the sink and the recommended cutout size. For example, a sink with an outer dimension of 600 × 500 mm may have a recommended cutout of 560 × 460 mm. This difference is due to the rim width – usually 18–25 mm on each side. The cutout must be a few millimeters smaller than the rim-defined opening so that the sink sits stably.

Procedure:

Place the sink upside down on the worktop exactly where it will stand
Outline the outer edge of the rim with a pencil
Then move inward by 18–20 mm (according to the rim width) and draw a cutting line
Drill holes of 10–12 mm diameter at the corners of the cutout as starting points for the saw
Cover the surface of laminated materials before cutting – this reduces the risk of chipping
Cut slowly, without pushing, with support for the cut-out piece (to prevent it from falling and breaking the edge)

How to measure the cutout for undermount installation

This situation is different – the cutout must be created exactly according to the template provided by the manufacturer, because with undermount installation you see the edge of the cutout. Alveus provides a plastic mounting template with some models directly in the packaging. If not, draw the cutout according to the dimensions listed in the technical documentation of the model. With undermount installation, the edge of the cutout is usually sealed with silicone before the sink is installed – this protects the wood from moisture.

Mounting an Alveus sink (topmount) – step-by-step procedure

This is a standard method that can be handled by an experienced DIY enthusiast. I assume the cutout is ready and the worktop is installed.

Step 1: Preparing the sink before placing it into the cutout

Before placing the sink into the cutout, install all components that you would not be able to reach or it would be very inconvenient after installation:

Faucet – slide on the gasket, insert the faucet into the hole in the sink (standardly Ø35 mm for a single-hole faucet), and tighten the compression nut from below. If you are buying a set, such as SET ALVEUS CADIT 40/55 + BATERIE RUTA CHROM, the faucet is sized directly for the sink hole and the gasket is part of the package.
Drain stopper (strainer) – insert the rubber gasket into the drain hole of the sink, slide on the drain basket, and from below, tighten the locknut. Tighten by hand, slightly with a wrench – over-tightening the gasket is undesirable.
Overflow valve – if the sink has an overflow, install its cover.

Step 2: Applying silicone to the sink rim

Apply a uniform bead of silicone about 5–6 mm thick to the underside of the sink rim. The silicone must be continuous around the entire perimeter. Use a neutral transparent kitchen silicone – not acetic (which smells and may corrode some surfaces). For granite sinks and stainless steel sinks with a dark surface, use dark or transparent silicone so it is not visible.

Step 3: Placing the sink into the cutout

Carefully (ideally two people for larger models) insert the sink into the cutout. Check that it is symmetrically centered. Gently press down – the silicone will spread under the rim and form a seal. Immediately wipe away any excess silicone with a damp cloth while it is still fresh.

Step 4: Securing with clips

From inside the cabinet, attach the mounting clips (included with every Alveus sink) to the rim, thread the screws through, and start tightening alternately from both sides – just like tightening wheel nuts on a car. Do not over-tighten the clips, just evenly press the rim against the countertop. The total number of clips depends on the model – a smaller sink (e.g., up to 500 mm) has 4 clips, a larger one (e.g., 800–1000 mm) has 6–8 clips.

Step 5: Connecting the trap

Connect the trap only after the sink is installed. Place the gasket on the drain basket, thread on the trap neck, connect the drain hose to the waste pipe in the wall. Adjust the length of the waste hose so that the slope is at least 2–3 % (2–3 cm height per 1 m length). A horizontal waste line without slope causes odors and clogs.

Step 6: Connecting water and leak test

Connect the braided hoses (flexible supply lines) to the faucet outlets and to the shut-off valves for hot and cold water. Tighten by hand, then with a wrench – 1.5 turns after hand-tight is sufficient. Open the supply, fill the sink, and check all connections. Fill the drain and observe the trap and waste hose. Let the leak test run for at least 10 minutes.

Undermount installation of Alveus sink – installation procedure

Undermount installation is technically more demanding, but the result is aesthetically on a completely different level. In practice, it is most commonly seen with stainless steel sinks in modern kitchens with stone or compact laminate countertops. This type of installation is ideal for the INTERMEZZO series, which is also available as a complete set – SET ALVEUS INTERMEZZO 130/81 + BATERIE TONIA Chrom or the more compact SET ALVEUS INTERMEZZO 30/91 + BATERIE DELOS 91.

Preparation and sealing of the cutout edges

After cutting the cutout, it is necessary to immediately treat the edges – MDF is hygroscopic and moisture quickly deforms it. Apply dispersion adhesive (e.g., D3 waterproof) or silicone to the edges twice. Let it dry according to the manufacturer’s instructions (usually 30–60 minutes).

Mounting system for undermount installation

The sink is attached to the underside of the countertop using two systems:

Mounting clips with rod – clips are placed along the edge of the sink, the rod passes through the countertop upwards, where it is secured with a nut. This system is common with stone countertops, where holes are drilled into the side of the countertop.
Adhesive brackets – for laminate countertops, epoxy brackets are glued to the underside of the countertop, to which the sink is hung or fastened with screws.

Always work according to the installation instructions for the specific model – Alveus provides specific hardware for sinks intended for undermount installation.

Replacement installation – replacing an old sink

Replacing a sink is the most common reason people look for installation instructions in practice. The worktop is original, the cutout is already there, and you need to fit a new sink into it. Here are a few scenarios I encounter most often in practice.

Scenario A: Same dimensions, different model

This is the easiest situation – the old sink has the same external dimensions (or the new sink’s rim is larger than the cutout) and the new sink fits perfectly. Procedure: cut the silicone, loosen the clips, lift the old sink, clean the surface of the old silicone (using a scraper and acetone), apply new silicone, place the new sink, and tighten the clips again. The water supply and trap usually remain – you just need new seals.

Scenario B: New sink is larger – cutout needs to be adjusted

If the new sink is larger, you need to enlarge the cutout. For laminate worktops, you can use a router; for stone worktops, you need an angle grinder with a diamond blade – or a stone company. Don’t forget to finish the new edges of the cutout.

Scenario C: New sink is smaller – problematic

If the new sink is smaller, the rim won’t cover the old cutout. Solutions: cover the gap with a decorative strip, use silicone and paint (not very aesthetic and temporary), or replace the worktop. In practice, you can easily avoid this scenario by carefully comparing the dimensions before buying a new sink. The article What sink size do I need – how to measure the worktop before purchase will help you with that.

Disconnecting the old sink – practical tips

Close the water supply shut-off valves (or the main shut-off valve) before starting work
Disconnect the flexible hoses with pliers, have a bucket ready – residual water is normal
Disconnect the trap from the waste pipe
Cut the old silicone with a sharp knife or a special silicone cutter along the entire rim
Loosen the clips (access through the cabinet hole) and lift the sink up
Clean the worktop surface thoroughly before applying new silicone – new silicone does not adhere to old silicone

Trap installation and drain connection – detailed instructions

The trap is where most amateur installations later show leaks. In practice, I have seen situations where the trap was physically mounted, but it leaked within two weeks because the seal was not properly installed or was completely omitted.

Types of traps for sink basins

Bottle trap – most common, easy to maintain (cleaning the bottle), lower drainage capacity
Tubular trap – higher flow rate, suitable for double sinks or sinks with large basins
Pop-up trap – the drain valve opens/closes via a lever mechanism, more aesthetically clean. This type is integrated, for example, in ATROX 50 černý 91 + pop up sifon.

Trap installation procedure

Insert the rubber seal into the sink’s drain basket (usually the upper seal is flat, the lower one is beveled). Slide the drain basket from above, place another seal from below, and manually screw on the trap nut. Tighten with a wrench – just about 1/4 turn beyond hand-tight is enough to compress the seal, but not so much that the rubber tears. Connect the trap hose to the waste pipe side with Teflon tape (if the tape is not part of the seal) – this depends on the material and type of connection. Check the slope of the waste hose with a spirit level.

Installation of a Faucet into a Sink – What You Need to Know

Faucets can be installed into a sink either before the sink is mounted (ideally when the sink is upside down on the countertop) or through an opening in the cabinet after installation. Álveus sinks have one standard 35 mm diameter hole for the faucet by default. Some models also have an additional hole for a soap dispenser or a secondary faucet.

With sets such as SET ALVEUS INTERMEZZO 30/91 + BATERIE DELOS 91, the faucet is specifically designed for the given hole – the gasket and mounting nut are included. During installation, thread the mounting rod or tube through the hole, place the gasket, attach the flange and nut. Tighten with a wrench so that the gasket is compressed, but not over-tightened – this is critical for stainless steel sinks, as over-tightening can deform the surface. It is sufficient to use hand force with a wrench on the faucet nut, no pipe extensions are needed.

Flexible supply hoses (hot and cold water inlet hoses) should be threaded by hand onto the threaded part of the faucet and then tightened 1/4 turn with a wrench to the stop. On a new faucet, the hose gasket is seated in a conical seat – no additional gasket is needed here, as the cone itself seals. Teflon tape is not required for conical connections.

Special Cases and Professional Notes from Practice

Sink in a very narrow cabinet (e.g. 40 cm)

The model ZOOM 10 NAT is an example of a narrow sink for tight spaces. When installing in a 40 cm wide cabinet, you have little room to maneuver. Use a special wrench with a short arm or an adjustable wrench with an offset. Flexible hoses must not be too long – in a narrow cabinet, they can easily kink (blocking the water flow). I recommend hoses with a maximum length of 35 cm for a cabinet depth of 50–55 cm.

Installation into a stone countertop

Granite, marble and quartz are materials for which both undermount and topmount installation must be discussed with the countertop supplier. The cutout is made directly by the countertop manufacturer, not on site. Silicone used with stone countertops must be special – a fungicidal kitchen silicone resistant to moisture. Stone countertops are not treated with D3 adhesive, but with stone impregnator.

Double sinks – specific siphon connection

Double sinks with two basins are usually connected with one siphon using a calibrated connecting "basket". It is important that both drain baskets are at the same height – otherwise, one will always be slightly clogged with waste from the other. The siphon for double sinks has a larger spring and a bottle with a 50 mm diameter instead of the standard 40 mm. Check the drainage capacity if you have tiles in the basin – a new waste line in the wall must handle a higher flow. More about choosing the right model can also be found in the article Simple or double sink – which one is suitable for your kitchen.

Sealing for sinks near a window or heat source

Silicone ages faster under extreme temperatures. For sinks under a window exposed to sunlight, I recommend UV-stable neutral silicone. Standard kitchen silicone under long-term direct UV exposure will crack after 5–7 years. Near heat sources (e.g. a built-in dishwasher next to the sink), use silicone with temperature resistance up to +120 °C.

Common installation mistakes and how to avoid them

Opening too small – the sink cannot be installed, it needs to be expanded. Always follow the recommended cutout dimensions from the documentation, not the outer dimensions of the sink.
Silicone applied to a dirty surface – it will not adhere and will leak water after a few months. The surface must be dry, clean and degreased with acetone.
Over-tightening the siphon gasket – the rubber will tear or extrude, and the siphon will leak. Tighten only by hand plus a small turn with a wrench.
Drain without slope – water will pool in the pipe, organic matter will decompose and odors will develop.
Flexible hoses without Teflon tape at the threaded connection – some connections require Teflon (parallel threads), others do not (conical). Mixing systems causes leaks.
Not respecting the silicone drying time – if the silicone is not fully dried (minimum 24 hours at room temperature), it may lose its sealing function under water pressure.

Frequently asked questions (FAQ)

Do I have to replace the shut-off valves completely during sink installation, or are the original ones sufficient?

The original valves are usually sufficient if they are functional and do not leak. I recommend checking them during the process – turn them on and off to clean the interior and remove lime deposits. If the valve leaks or is stiff when closed, replace it. When replacing the sink, always perform the flexible hose connection with a bucket underneath the valve.

Can I install an undermount sink myself, or is a professional necessary?

It depends on the countertop. With a laminated countertop and sufficient manual skills, you can do it at home. With a stone countertop (granite, marble, quartz), the cutout must be made by the countertop manufacturer – cutting stone on site without water cooling is very difficult and may cause the countertop to crack. Attaching the sink after the countertop with a cutout is again manageable by yourself.

How long do I have to wait before using the sink after installation with silicone?

A minimum of 24 hours at a temperature above 18 °C and relative humidity below 70 %. In cold or humid conditions (e.g. autumn/winter, poor ventilation), extend to 48 hours. Silicone dries on the surface within 30–60 minutes, but the inner mass hardens more slowly. Premature loading with water will cause the silicone to lose its sealing function.

What if the mounting bracket does not reach – the sink moves?

If the bracket does not reach the edge sufficiently, use an additional washer or a longer screw. Some cases occur when the worktop is too thick (e.g. 60 mm stone). In such cases, contact the sink supplier – Alveus has extended brackets as accessories for some models. The sink must not be loose by even a millimeter, otherwise the silicone will crack when leaning on the sink.

Is it necessary to replace the siphon when changing the sink?

Not always. If the old siphon is functional, the gaskets are not grayed or hardened and you have no odors from the drain, you can keep it. However, when replacing the sink completely, I recommend a new siphon – they are cheap (5–20 €) and will save you from possible further disassembly. Check the compatibility of the drain opening diameter – standard is 63.5 mm (European) or 90 mm, some sinks have a different standard. Check the technical documentation of the model.

Can I use any silicone, or is a special type required?

You must use neutral kitchen silicone with a fungicidal additive (anti-mold). Acetic silicone (smells like vinegar) can damage some surfaces including aluminum and galvanized parts. For dark granite sinks, use black or dark gray silicone – white would be visible. Function: the silicone must be flexible (not rigid construction silicone), moisture-resistant, with temperature resistance of at least -20 °C to +90 °C.

Conclusion: Sink installation as an investment in quality and long life

Proper installation of an Alveus sink is not just a technical formality – it is the foundation for the sink to serve for decades without leakage, odors or loosening. Most problems I encounter during service visits stem from three errors: insufficiently cleaned surface before silicone application, over-tightened siphon gaskets and a drain without slope. If you avoid these three errors and proceed systematically according to the instructions, you can install the sink at home by yourself – whether it is a new kitchen, replacing an old sink or changing from topmount to undermount installation.

For a deeper understanding of choosing the right model, I recommend the articles Alveus granite sink vs. stainless steel sink – comparison of properties and maintenance and Installation of an Alveus granite sink – installation procedure including siphon and faucet, where you will find further specifications you need to know when working with granite sinks.

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