Installation of stainless steel hose under the sink or to the faucet
Installation of a stainless steel hose under the sink or to the toilet – complete practical guide
Replacing or installing a connecting hose under the sink, to the toilet cistern or to the faucet is one of the most common plumbing tasks that every household owner and experienced technician encounters. At first glance, it seems to be a trivial matter – just screwing the hose on for two turns. In practice, however, most leaking connections, cracked plastic hoses after years of operation and unnecessarily paid emergency plumber visits over the weekend arise precisely here. This article will guide you through the entire process from choosing the right hose to the final sealing check – so that you do it once and correctly.
What you will need before starting the installation
Before you open the cabinet under the sink or reach for the wrench, it is worth doing a short preparation. From my own experience, I know that most complications during installation do not arise during the installation itself, but precisely because someone bought the wrong hose or forgot to turn off the water before removing the old one.
Tools and materials
- Adjustable wrench (spanner) or combination wrench 24–27 mm
- Teflon tape (PTFE) or hemp fiber + thread sealing paste
- Plastic tray or cloth to catch residual water
- Flashlight or headlamp (there is usually a lack of light under the sink)
- Tape measure or sliding caliper to measure the required length
- Pencil and paper to mark the thread dimensions
Turn off the water BEFORE any work
This sounds obvious, but in practice, I have encountered cases where someone started to loosen the old hose without turning off the angle valve. The angle valve (ball valve) is located directly under the sink or behind the toilet cistern – it is a small valve with a handle that closes the water supply to the specific appliance when turned 90°. If the valve does not work, is missing or is stiff, you must turn off the main water shut-off valve for the apartment or house.
How to determine which hose suits you – dependency on thread, length and type of fitting
This is the step where people make the most mistakes. They buy the hose "at a glance" and at home find out that the thread does not fit or the hose is 10 cm shorter than needed. Spend 5 minutes on this point and save yourself a second trip to the store.
Thread: 3/8" or 1/2"?
In most Slovak and Central European households, you will encounter two basic threads on connecting hoses: 3/8" and 1/2". The 3/8" thread (read "three eighths of an inch") is typical for connecting hoses to sink and kitchen faucets, where the water flow is smaller. The 1/2" thread (half an inch) is common for toilet cisterns, shower faucets or where the angle valve has a larger diameter.
How to determine it without a measuring tool? Look at the old hose – the thread size is usually engraved directly on the metal nut. If there is no old hose, measure the outer diameter of the angle valve thread: 3/8" corresponds to a thread diameter of about 16.7 mm, 1/2" is about 20.9 mm. A more detailed guide can be found in the article Thread 3/8" or 1/2" – how to determine what you need in our Knowledge Center.
Important: hoses in this category are mostly FF (female-female, i.e., both sides internal thread) – this means that both nuts are "female" and you screw them onto the external thread of the angle valve and the external thread of the faucet. This is the standard solution for the vast majority of common installations.
Length: how to measure it correctly
The most common mistake: people measure the direct distance between two connections and order the hose accordingly. That is not enough. The hose does not lie in a straight line – it must form a slight arc so that it does not bend, does not stretch and can be easily screwed. I recommend adding at least 10–15 cm to the direct distance. If the distance is 35 cm, take a hose of at least 45–50 cm.
For greater flexibility, extendable hoses are ideal, covering a range of lengths – for example from 30 to 60 cm or from 50 to 100 cm. More on this topic can be found in the article What hose length suits me – fixed or extendable?
Types of stainless steel hoses – what the different variants mean in practice
You can find several versions of stainless steel connecting hoses on the market, and it is important to know how they differ to avoid buying something unsuitable for your type of installation.
Bare stainless steel hose vs. hose with plastic coating
A bare stainless steel hose (pure stainless steel without any additional coating) is resistant to mechanical damage, looks aesthetically pleasing and does not attract bacteria on the surface. The plastic coating on a stainless steel hose is intended to protect the spiral from being caught on sharp edges of fittings and also prevents condensation on the surface in cold environments. For regular use under a sink, the difference is minimal, but in colder areas (cold winter, unheated hallway), a plastic coating may be more practical. More about this difference can be found in the article Stainless steel hose with plastic coating vs. bare stainless steel – which one is better.
Stainless steel vs. brass fittings
The fittings (nuts) of the hose can be either made of stainless steel or brass (sometimes chrome-plated). Stainless steel fittings are more resistant to corrosion, do not release heavy metals into the water, and are suitable for installations for drinking water. Brass fittings are slightly softer and therefore easier to seat on the thread without the risk of thread stripping – however, if a stainless steel nut is improperly gripped with a wrench, the shape will not be damaged. A detailed comparison can be found in the article Stainless steel vs. brass fittings – what is the difference and what to choose.
In the atria.sk range, you can find for example Stainless steel adjustable hose PROFI S for drinking water with stainless steel fittings (1/2" FF, 50–100 cm) – this hose has full stainless steel fittings and is suitable wherever you want maximum resistance and certified safety for drinking water. For installation to standard sink taps with a smaller thread, the Stainless steel adjustable hose PROFI MW (3/8" FF, 30–60 cm) with plastic coating and brass fittings is used – a practical solution where you need to cover a shorter distance with a shorter dependency on the 3/8" thread.
Step by step: installation of a stainless steel hose under the sink
We will now move on to the actual installation process. I will assume you are replacing an old (plastic or old stainless steel) hose with a new stainless steel one. The procedure for the first installation is identical, just skip the steps involving the removal of the old hose.
Step 1 – Closing the water and draining
Turn the handle of the angle valve perpendicular to the pipe axis (by 90°). Open the tap to drain the remaining water from the hose and reduce the pressure. Place a plastic bowl under the work area – old hose and angle valve will always release several deciliters of water.
Step 2 – Removing the old hose
Use a wrench to loosen the nut on the angle valve (turn to the left, i.e. counterclockwise when viewed from above). Then loosen the nut on the tap connection as well. Be careful: if the hose is old and stiff, the nuts may be carbonized or stuck with limescale. Do not use brute force – rather use WD-40 or a similar product and let it work for 10–15 minutes.
During disassembly, notice what type of sealing (gaskets) were used in the old connections. Usually, these are rubber O-rings or flat rubber seals. New stainless steel hoses usually come with new seals – despite this, I recommend checking whether the seal is properly seated in the nut before installation.
Step 3 – Preparing the threads
Check the thread on the angle valve and on the tap connection. If you see remnants of old Teflon, old seals or corrosion, carefully remove them. The threads must be clean and undamaged. You do not need to wrap the external thread of the angle valve with Teflon (PTFE tape) if the hose uses a rubber gasket as a seal (which is standard in this case) – the sealing is done by seating the rubber gasket into the thread face, not by wrapping the thread with tape. Teflon tape is used for conical connections or for straight threads without a gasket seal. If you are unsure, read our article Why the hose drips or leaks at the connections – causes and repair.
Step 4 – Mounting and tightening the hose
Before mounting the nut on the thread, make sure that the rubber gasket (seal) is properly seated in the nut and has not fallen out. Start tightening the nut by hand (without a wrench) – at least 2–3 turns until you feel that the nut is seating evenly. This is called "manual pre-tensioning" and prevents thread distortion.
Then tighten the nut with a wrench by an additional 1.5–2 turns beyond the manual pre-tensioning. Do not over-tighten – with stainless steel hoses using rubber sealing, a relatively small force is sufficient. An over-tightened nut can crack or deform the seal, paradoxically causing a water leak.
Step 5 – Repeat the same procedure on the other side (tap connection)
Repeat step 4 on the other end of the hose – on the tap connection. Here, the threads are usually smaller (3/8" for sink taps) and the space is sometimes tight. If the hose is adjustable, set its length so that it forms a slight arc – not tightly in a straight line and not so loose that the hose touches the trap or other elements under the sink.
Step 6 – Opening the water and checking the seal
Carefully open the angle valve. Do not stand right next to it – monitor both connections for at least 2–3 minutes. If there are no drips, open the tap and let the water run for at least one minute at full flow. Check the connections again. If you see drops or moisture, immediately close the valve and tighten the connection by an additional quarter turn. If the dripping continues, it is necessary to unscrew the connection and check the seal – the rubber gasket is likely shifted or missing.
Specific situations and common problems from practice
The hose is too short
This happens when the angle valve is located far from the faucet or when the customer ordered a "by eye" hose without measuring. The solution is an extendable hose with a larger length range. For larger distances, I recommend for example Stainless steel extendable hose PROFI MW (1/2" FF, 80–160 cm) – it covers a really wide range and is also useful in installations where the connection is further from the device, for example with corner sinks or non-standard mounted faucets.
Never use a stretched hose – connections under constant tensile stress will break faster and seals will wear out faster. The hose must always have a reserve in the bend.
Threads do not fit – different sizes
If the angle valve has a 1/2" thread and the faucet accepts 3/8", the solution is a reducer or a hose with different ends (one end 1/2", the other 3/8"). Standard "FF" hoses have both ends the same – in such a case you need either a different hose or a brass reducer. Always check both sides of the installation before purchase.
Old connection cannot be unscrewed
10–20-year-old nuts are often "rooted" due to limescale deposits or corrosion. Procedure: apply a loosening agent (WD-40 or a specialized connection loosening agent), wait 15–20 minutes, and try again with a wrench. Never use an extension bar on the wrench, as with old plastic hoses and angle valves there may be a break. In the worst case, it is necessary to replace the angle valve – a job for a plumber.
Condensation on the hose surface
If you have cold water and a warm environment, air humidity can condense on the surface of the stainless steel hose – this is not a leak, just condensation. The solution is a hose with a plastic cover, which has better surface insulation.
The hose does not fit due to a trap or other elements
Under the sink, it is sometimes really tight – the trap, drain pipe and connecting hoses are all competing for space. Here it pays off to use a shorter extendable hose or choose a hose with greater flexibility (greater length reserve). For example, Stainless steel extendable hose PROFI MW (1/2" FF, 40–80 cm) provides enough space for optimal routing even in tight conditions.
Installation of the hose to the faucet – procedure and specifics
Installation to the faucet itself (especially for a wall-mounted sink) is slightly different from connecting to a WC flush valve or a shower faucet. The faucet usually has one or two outputs (for hot and cold water) with an external thread of 3/8" on the bottom side. The connecting hoses are screwed directly to them – either via the faucet connections or directly to the body of the faucet, if the threads are accessible.
Be careful with wall-mounted faucets with long bodies (faucets with long connecting tubes, e.g. ceramic or floor-standing faucets): the connections are often shifted and the distance to the angle valves can be non-standard. Again, I recommend extendable hoses with a larger length range.
The procedure is the same for kitchen faucets – there we also encounter hoses for filtered water (with three-way taps), but they are thinner and have different threads (5/8" or 1/4") – that is a different story.
Certification and suitability for drinking water
Not every hose sold as "stainless steel" is certified for contact with drinking water. If you are connecting water supply to a kitchen sink or a drinking water tap, the hose must meet the appropriate hygiene requirements (certificates according to STN, DIN DVGW, WRAS, etc.). High-quality PROFI series hoses intended for drinking water have these certificates – always check them in the product technical documentation before purchase. A more detailed discussion of this topic is in the article Stainless steel hoses and drinking water – certificates, non-harmfulness, what to watch for.
Lifespan of a stainless steel hose and when to replace it
A stainless steel hose is significantly more durable than the original plastic (EPDM or rubber) hoses that were the standard 20 years ago. While a plastic hose can crack and break after 5–8 years, a quality stainless steel hose has a lifespan of 10–20 years under normal operation. Despite this, I recommend a visual inspection at least once every 2 years – check for visible corrosion at the connections, damaged braiding or hardening of the seal. More on this topic can be found in the article How long does a stainless steel hose last and when to replace it.
If you are carrying out a bathroom or kitchen renovation and you remove the faucets, always replace the connecting hoses preventively – regardless of their age. A new hose costs a fraction of the cost compared to the damage caused by a burst hose, and when you have the space open, it is an additional 10 minutes of work.
Most frequently asked questions (FAQ)
Do I always have to change the seals when replacing the hose?
New stainless steel hoses come with their own seals (rubber washers in the nuts) and these are usually pre-installed by the manufacturer. Do not reuse the old seals from the previous hose – they are worn and may be hardened or deformed. If you were to use an old seal on a new hose, you risk a water leak right after the first opening. Always use the seals that are part of the new hose's packaging.
Can I bend the hose into a sharp angle if the space requires it?
No. A stainless steel braided hose has a minimum bend radius – if bent too sharply, the inner rubber layer (EPDM) can be compressed, which restricts flow and long-term damages the hose. The minimum recommended bend radius is usually 5–8 times the outer diameter of the hose (for a standard 1/2" hose this is about 6–10 cm). If the space really does not allow it, use intermediate elbows or choose a shorter hose with a different routing.
What to do if the connection still drips after tightening the nut
First, close the valve and unscrew the connection. Check whether the rubber gasket is correctly positioned in the nut, not shifted or cracked. If the sealing looks fine, check the external thread of the angle valve – it may be damaged or have dirt. If the thread is in order and the sealing is also fine, try tightening the nut by an additional quarter turn. Repeated dripping despite a correct sealing may indicate a damaged thread or a faulty nut – in this case, replacement is necessary. More information can be found in the article Why the hose drips or leaks at the connections – causes and repair.
Can I use the same hose for hot and cold water?
Yes – standard stainless steel connecting hoses for drinking water are certified for a medium temperature up to 90 °C (some up to 120 °C), which covers normal hot utility water (40–60 °C). For hot water distribution systems above 70 °C, always check the maximum operating temperature in the technical documentation of the specific hose. In a standard apartment installation, there is nothing to discuss – every hose from the PROFI range handles it without any problem.
What pressure must the hoses withstand?
The operating pressure in residential water supply installations in Slovakia is usually 2–6 bar, occasionally up to 8 bar. Quality stainless steel connecting hoses are dimensioned for a minimum operating pressure of 10 bar and a test pressure of 15–25 bar. This is more than sufficient for any household. Further information on pressure and other technical parameters can be found in the article Common questions about stainless steel hoses – threads, lengths, pressure, replacement.
Is there a difference whether I install it myself or through a plumber?
Technically, no – replacing a connecting hose is a relatively simple task that any handy amateur with basic tools can manage, provided the correct procedure is followed. Legally: if a failure occurs and results in property damage (e.g., flooding neighbors), the insurance company may investigate who performed the installation and whether it was done correctly. If you are unsure, call a plumber – replacing one hose is a 15-minute job for them and the cost will be reasonable.
Conclusion – a few practical tips at the end
Installing a stainless steel connecting hose is not rocket science, but it requires attention to detail: the correct thread size, the correct length, new sealing, not over-tightened nuts, and a thorough check after turning on the water. If you follow all these steps correctly, the new stainless steel hose will reliably serve you for ten or more years without any further intervention.
If you are looking for a specific product, in the category stainless steel hoses you will find at atria.sk a complete range for various threads, lengths, and types of installations – including certified hoses for drinking water with stainless steel or brass ends, bare or with plastic cover, in compact and extended dimensions. Always carefully check the thread size on both sides of the installation and measure the required length including the curved reserve before ordering.
Do you have a question about this topic?
Having trouble deciding or dealing with a specific situation in your home? Write to us – we are happy to help.