Head Diameter and Thread: How to Determine the Correct Dimensions Before Ordering

We are still preparing products.

But you can look at other categories.

Head Diameter and Thread: How to Determine the Correct Dimensions Before Ordering a Replacement Part

One of the most common problems customers encounter when ordering replacement parts for bathroom taps is the incorrect determination of the head dimensions – that is, the diameter and type of thread. At first glance, it seems to be a simple task: unscrew the old shower head, measure it, and order the same one. In practice, however, it looks different. Taps from different manufacturers, different generations of the same models, non-standard threads, and confusion in labeling cause many customers to order a part that fits "almost, but not quite" – and then there is a problem with tightness, with the thread twisting, or with the part simply not fitting.

This article will take you through the entire process: from basic concepts, through practical measurement, to how to verify compatibility even before you click "Add to Cart". If you are not sure whether this topic is relevant to your tap, also check the related articles in our Knowledge Center – specifically How to Choose a Replacement Shower Head – What to Pay Attention to and Compatibility of Replacement Parts: Does a Universal Shower Head Work in Every Tap.

What is a "thread" and why it matters

A thread is a spiral groove cut into the outer or inner surface of a pipe or fitting. It allows for mechanical connection of two parts by turning – in the case of bathroom taps, it is most often the connection of the hose to the shower head or the connection of the supply hose to the body of the tap. It depends on two basic quantities: the thread diameter and the thread pitch (the distance between two threads).

In plumbing and water supply installations, the following types of threads are mainly used:

G (BSP – British Standard Pipe) – the most widespread type in European plumbing. It is a cylindrical thread with designations such as G 1/2", G 3/4", G 1". The number after G indicates the nominal diameter in inches, but note – this number is not the actual outer diameter of the thread. G 1/2" has an actual outer diameter of approximately 20.9 mm.
M (metric thread) – designations such as M22×1. The number after M is the actual outer diameter in millimeters, the number after the slash is the thread pitch in mm. The metric thread M22×1 is typical for shower hoses and connectors.
NPT (National Pipe Thread) – an American conical thread, rare in European plumbing, but sometimes appears in imported products.

For the average customer, it is important to know that G 1/2" (BSP) and M22×1 are two completely different threads, although their outer diameters are very similar (20.9 mm vs. 22 mm). These two types cannot be screwed together – neither the groove pattern nor the pitch is compatible. This difference causes a huge number of complaints when the customer "by force" puts one type on the other and the result is a deformed thread or a leak.

Head diameter: what exactly to measure and how

When we talk about the "head diameter" in the context of replacement shower heads and bathroom taps, we usually mean two different things: the outer diameter of the shower head body (the overall diameter of the head body, e.g. 80 mm or 120 mm) and the diameter of the connecting thread – that is, the place where the hose is screwed onto the shower. These two values must not be confused.

Outer diameter of the shower head body

This is a dimension that mainly affects aesthetics and comfort, not functionality. Shower heads have diameters ranging from 60 mm (compact, travel) to 200 mm and more (rain effect). A standard handheld shower in a tap (not a rain shower on top) usually has a diameter of 70–100 mm. When ordering a replacement shower head, this number is not critical in terms of fit – it will only affect the feeling of showering and the water volume.

Diameter of the connecting thread – this is the critical dimension

The connecting thread is the place where the hose is attached to the shower. In the vast majority of cases, it is M22×1 – a metric thread with an outer diameter of 22 mm and a pitch of 1 mm. This dimension is de facto an industry standard for shower hoses and handheld showers in European plumbing. This applies to almost all showers sold on the Slovak and European markets.

There are, however, exceptions:

Some older taps (manufactured before the year 2000) may have non-standard threads or different pitches.
Imported goods from Asia (especially cheap taps without certifications) sometimes use M24×1 or even M18×1.
Premium brands sometimes produce their own patented connections, which are compatible only with their own hoses.
Taps with built-in (fixed) outlets instead of hoses – there the shower is connected directly to a fixed pipe and the thread can be G 3/8" or other.

How to measure the thread correctly? You need a caliper or at least an accurate ruler. Measure the outer diameter of the thread at the end of the shower where the hose is attached. If you don't have a measuring tool, compare visually with a coin: the M22 thread has a diameter almost exactly the same as the diameter of a 2-euro coin (25.75 mm is the diameter of the coin, so the M22 thread will be slightly smaller).

Thread identification without a caliper – practical methods

Not everyone has a caliper at home. The following methods will help you determine the type of thread even without a precise measuring tool, or at least confirm what you probably have.

Method 1: Check the battery documentation

The fastest and most reliable method. If you have an installation manual, technical sheet, or box for the battery, the dimensions of the connection are usually listed there. Look for markings such as "connection: M22×1" or "shower: M22 thread". If you don't have paper documentation, look up the battery model on the manufacturer's website – technical sheets are usually available in PDF format.

Method 2: Try to fit a standard hose nut

If you have an old shower or a hose nut with an M22×1 thread (for example, from a replaced hose), try to fit it onto the thread of your battery. If it easily slides on and turns (without force), you have M22×1. If it doesn't fit at all, the thread is different.

Method 3: Width of the wrench flat

A shower nut (hexagonal) on an M22×1 thread usually has a wrench width of SW24 or SW27. If you place the appropriate wrench and it fits – you're on the right track. Note: this will tell you the width of the nut, not the thread itself, but since the nut and thread are designed together, it is a good indicator.

Method 4: Take a photo and consult a seller

Take a photo of the threaded part of the shower or hose connector from several angles – best with a focus (a ruler next to the part). A good photo with a numerical comparison will tell most experienced sellers immediately what kind of thread it is.

Differences between internal and external threads – where customers get confused

Another common source of confusion: external thread (AG – Außengewinde) versus internal thread (IG – Innengewinde). An external thread is cut on the outer surface of a rod or pipe – you can see the grooves from the outside. An internal thread is cut into the inside of a hole – the grooves are hidden.

In bathroom taps, the following arrangement is common:

The hose has internal threads M22×1 on both ends (screws onto the external thread of the shower and the external thread of the tap).
The shower has an external thread M22×1 at the end of the neck.
The tap outlet (hose connection) has an external thread M22×1 or G 1/2" depending on the design.

This arrangement is standard, but there are taps where the arrangement is reversed – for example, in fixed shower holders with a hidden hose. In such cases, carefully read the technical specifications of the replacement part before ordering.

Concrete examples from practice: what customers often overlook

Over years of experience in selling replacement parts, we have encountered several typical scenarios that lead to ordering the wrong part. Here are the most common ones:

Example 1: The customer confuses the body diameter of the shower with the thread diameter

Mrs. Marta wants to replace a broken shower in her bathroom. She measures the old shower from edge to edge – she gets 85 mm. She orders a "shower with a diameter of 85 mm". However, the manufacturer of her new shower lists "diameter 85 mm" as the outer diameter of the body – but the thread is M22×1, the same as in every other shower. So in this case, everything works out fine. Problems arise when the customer instead measures the diameter of the threaded part (22 mm) and looks for a "shower with a 22 mm diameter" – and gets confused during the search.

Lesson: the body diameter and the thread diameter are two different things. The body diameter determines the size of the shower, the thread diameter determines compatibility. For replacement showers, M22×1 is almost always the case – this dimension is rarely mentioned separately by most sellers, as it is standard.

Example 2: Tap with a non-standard outlet

Mr. Vladimír has a Chinese-made tap bought eight years ago at a market. His shower started to leak and he wants to replace it. He buys a standard replacement shower M22×1. He tries to fit it – it doesn't work. He measures the thread: 18 mm. He has a tap with an M18×1.5 thread – a non-standard dimension that occasionally occurs in cheap Asian products. In this case, the solution is either to find a special adapter (M18 to M22), or to replace the entire tap with a standard one.

Example 3: Shower on a sensor tap – different construction

The Kováč family has a touchless tap with an infrared sensor. The shower stopped spraying evenly, so they decided to replace it. Before ordering anything, it is important to check whether it is a manual shower (on a hose) or a fixed rain shower (fixed outlet). Touchless taps often do not have a manual shower at all – they have only one outlet with a flow restrictor or a fixed rain shower. In such a case, a replacement shower is not ordered, but either a flow restrictor or the entire outlet module. If the tap also has a manual shower on a hose, the thread is again standard M22×1.

By the way – if you have a touchless tap and are having problems with the sensor, not with the shower head, check the Knowledge Center article Common faults of touchless taps and how to fix them with replacement parts and also Replacing the infrared sensor of a tap – step-by-step without calling a service technician.

Overview of standard dimensions for the most common types of taps

For quick orientation, we provide an overview of typical dimensions you will encounter with common bathroom taps available on the Slovak market:

Type of connection	Thread designation	Outer diameter	Where it occurs
Shower ↔ Hose	M22×1	22 mm	99 % of European showers
Hose ↔ Basin (outlet)	M22×1 or G 1/2"	22 mm / 20.9 mm	Depends on the manufacturer
Water supply (installation)	G 1/2"	20.9 mm	Angle valve, wall
Aerators	M22×1 (external) or M24×1	22–24 mm	Basin outlet spouts
Non-standard (Asia)	M18×1.5 or M20×1	18–20 mm	Cheap imported goods

How to identify the model of your basin to order the correct spare part

If you know you need a replacement showerhead, but are unsure about the thread size, the ideal solution is to find the exact model of your basin and order the spare part directly for that model. Most manufacturers of bathroom basins mark their products with a label or laser engraving on the body of the basin.

Where to look for the model marking:

On the bottom of the basin body (near the sink) – some manufacturers indicate the model number there.
On the supply valve or inside the handle (after disassembly).
On the hose – some brands mark the hose and the showerhead with their own number.
In the installation manual – if you have kept it in a folder with other documentation (which is strongly recommended by professionals).
On the invoice or delivery note from the original purchase.

For example, for Turin basins, there is an replacement showerhead for Turin TRN11102 – if you have exactly this model, you don't need to worry about measuring the threads, the part is specifically designed for it. Similarly, for Matera basin owners, there is an replacement showerhead for Matera MTA11101, or for MZ-Expo replacement showerhead for MZ-Expo MZE11106. Ordering a spare part according to the specific model of the basin is always safer than looking for a "universal" replacement.

What to do if you cannot identify the thread – step-by-step procedure

Sometimes a situation arises where despite all efforts you cannot accurately determine the type of thread. Here is the recommended procedure:

Remove the old part – without damaging it. Use the correct wrench or hose pliers with a protective insert (to avoid damaging the surface of the nut).
Measure the outer diameter of the threaded part using a caliper – record the number in millimeters.
Count the number of threads in 10 mm length – place a ruler along the axis of the thread and count how many grooves are in 10 mm. For M22×1 it is 10 grooves in 10 mm (pitch 1 mm = 10 threads/cm). For BSP G 1/2" it is approximately 5–6 grooves in 10 mm (pitch 1.814 mm).
Take a photo of the part with a ruler near the threaded part and send the photo to the seller together with the measured values.
Request identification – a good seller can tell you based on the photo and dimensions what kind of thread it is and which replacement part is suitable for you.

Special cases: infrared and touch basins

Touchless and touch basins (sensor-controlled) have a slightly different construction compared to classic lever basins. Their replacement parts are therefore identified a bit differently.

Infrared basins usually do not have a manual shower – their outlet is fixed, with an aerator. If the "damaged shower" does not spray – or does not even let water flow – the problem is usually not in the showerhead, but in the sensor, solenoid valve, or electronics. In this case, a replacement showerhead is not ordered, but a replacement sensor. For sensor basins in the FREE series, there is an infrared sensor replacement for FREE, and for the Classic series there is an infrared sensor replacement for Classic. Before ordering a sensor, also read the articles Infrared sensor vs. touch control – what type of basin do you have at home and Infrared sensor replacement – replacement without a service technician, which will help you confirm whether the sensor is actually the cause of the problem.

If the sensor faucet also has a shower outlet (a combined sink-shower unit), this outlet also has the standard M22×1 thread. Identification is the same as with regular faucets.

Sealing and its influence on the choice of the correct part

Along with the thread, the type of sealing is also important when replacing shower heads and connectors. Most showers have a flat rubber gasket on the end nut, which ensures a watertight surface. This gasket is part of the shower or hose – when replacing the entire unit, it will be included.

However, if you are only replacing the gasket (the hose is sealing, but the shower or connector is leaking), you must know:

Inner diameter of the gasket (to fit into the nut).
Thickness of the gasket (usually 2–3 mm).
Material – preferably EPDM (resistant to drinking water) over cheap NBR rubber.

Gaskets for M22 nuts have an inner diameter of 15–16 mm and an outer diameter of 21–22 mm. If you have problems with leakage despite the correct thread, check our article Why the shower head is leaking or dripping – causes and solutions.

Verifying compatibility before ordering – checklist

Before you click "order," we recommend going through this checklist:

✔ I know what type of faucet I have (sink, shower, touchless, touch, lever).
✔ I know my faucet model – or I have at least identified the manufacturer and series.
✔ I have confirmed whether my faucet has a handheld shower on the hose or only a fixed outlet.
✔ I have measured the thread diameter (or I know it is the standard M22×1).
✔ I have checked whether the thread is external (on the shower) or internal (on the hose) – and whether the ordered part is compatible.
✔ I have read the technical specifications of the replacement part – especially the type of thread.
✔ If I have doubts, I contact the seller before ordering, not after.

Most common ordering mistakes – and how to avoid them

Based on practical experience, we list the most common mistakes that occur when ordering replacement parts by dimensions:

Mistake No. 1: Measuring a worn thread. If the thread is damaged or deformed, the measurement will be inaccurate. Always measure an undamaged part or thread from the opposite side (e.g., the hose nut instead of the thread on the faucet, if the thread is damaged).

Mistake No. 2: Confusing "1/2 inch" with 12.7 mm. G 1/2" does not mean an outer diameter of 12.7 mm (= half an inch). It is only a nominal designation – the actual outer diameter of G 1/2" is 20.9 mm. This confusion causes a large number of misunderstandings.

Mistake No. 3: Purchasing based on a photo. Photos in e-shops are mostly representative – the shape and color may slightly differ from reality, but the thread is always the same (M22×1), unless stated otherwise. Do not try to estimate the diameter from photos.

Mistake No. 4: Ordering a "universal" shower without verification. Some showers are labeled as "universal," which usually means they have a standard M22×1 thread – but it does not mean they will fit any hose connector or faucet. The term "universal" is marketing, not technical. Always verify the thread. You can read more about this topic in the article Compatibility of replacement parts: does a universal shower fit every faucet.

Mistake No. 5: Ignoring the thread direction. Most threads in plumbing are right-handed (tightened clockwise). A left-handed thread is an extreme exception, but it can occasionally occur. If a part unscrews in the "wrong" direction – try the opposite direction before applying force.

FAQ – Frequently asked questions

How can I determine if my thread is M22×1 or G 1/2", since they look so similar?

The most reliable method is to count the number of thread grooves over a 10 mm length. M22×1 has 10 grooves in 10 mm (fine thread), while G 1/2" has only 5–6 grooves in 10 mm (coarse thread). If you have a caliper, measure the outer diameter: M22×1 = 22.0 mm, G 1/2" = 20.9 mm. The 1.1 mm difference is measurable with a standard caliper, but visually these threads are very similar – so never estimate just by sight.

Can I use any replacement shower if my thread is M22×1?

From a mechanical compatibility perspective, yes – any shower with an M22×1 thread will fit onto an M22×1 hose nut. However, be careful: some showers from specific manufacturers have special adapters or locking elements that limit the use of third-party parts. It also depends on the water flow (l/min) and the number of nozzles. For optimal results, it is always better to order a shower specifically for your faucet model, rather than just looking for "anything with M22."

What if the shower fits the thread but leaks after tightening?

The cause is almost always a damaged or missing flat gasket in the nut. Check whether the rubber washer is present and not broken, deformed, or hardened due to aging. Replace the gasket with a new EPDM one (available at any hardware store for a few cents). If the gasket is properly seated and the connection still leaks, check whether the thread is deformed due to excessive tightening during the previous installation.

I have an infrared faucet and no water is flowing – do I need a replacement shower?

Probably not. Touchless faucets are controlled by electronics and a solenoid valve. If no water is flowing at all, the problem is most likely the sensor, the valve, or the power supply – not the shower head. Try restarting the faucet (disconnect power for 30 seconds), clean the sensor, and check the battery voltage (if it is battery-powered). For a detailed diagnostic procedure, read Common faults in touchless faucets and how to fix them with replacement parts. For sensor replacement, see products such as replacement infrared sensor for FREE or replacement infrared sensor for Classic depending on your model.

Is it dangerous to replace the shower myself if I'm unsure about the thread?

It is not dangerous in terms of safety (water under domestic pressure of 2–4 bar is not life-threatening), but an incorrect thread can cause a leak and water escape, which can damage walls or floors if ignored for a long time. If the part turns easily for the first 1–2 turns and then starts to bind, stop immediately – you are likely cross-threading incompatible threads. For more on the replacement procedure, see the article How to replace a shower head in a faucet yourself.

Where can I find technical specifications for replacement parts before purchasing?

Technical specifications, including the type of thread, are listed for each product in the Replacement Parts section. If you are looking for a parameter and cannot find it, write or call – we are able to verify compatibility for a specific faucet model before ordering.

Conclusion: Measure twice, order once

Identifying the correct diameter and thread of the head is not rocket science – but it does require some attention and patience. In 90% of cases, the shower hose and head use the M22×1 thread, and the entire problem reduces to finding the correct faucet model and ordering the appropriate replacement shower. In the remaining cases – non-standard faucets, older types, or Asian products – it is necessary to physically measure the thread or consult with a seller.

A rule of thumb that always applies: never force a part onto a thread. If the correct thread fits, it will easily screw on by hand for the first two to three turns without resistance. If you feel resistance from the start, you either have the wrong thread or a dirty thread (limescale, corrosion). In that case, stop, verify the dimensions, and then proceed.

Correctly determined dimensions before ordering will save you time, unnecessary return costs, and most importantly, the frustration of a failed installation. A little preparation before purchasing is always a better investment than a rushed order.

Do you have a question about this topic?

Can't decide or are you dealing with a specific situation in your household? Write to us - we'll be happy to help.