| Item | Detail |
|---|---|
| Dominant thread | G1/2 (BSPP, ISO 228-1) parallel thread, 14 threads per inch and a major diameter of 20.955 mm, sealing on a washer or cone face rather than on the threads |
| North America | Shower arms commonly carry 1/2 inch NPT tapered thread; the hose supply end or an adapter is the conversion point |
| Adapter set | Four types, all G1/2 on the head side: S = M22.1 x 1.5, G = M21.3 x 1.5, K = M21.5 x 2, M = M22.1 x 1.75 |
| US flow rule | A federal maximum of 2.5 gpm at 80 psi commonly applies; WaterSense is voluntary at 2.0 gpm or less (specification version 1.1); California applies 1.8 gpm |
| Canada | The National Plumbing Code of Canada (2020 and 2025 editions) limits individual shower heads to 7.6 L/min, about 2.0 gpm; provinces adopt the code with their own amendments |
| Europe | No single national flow ceiling for shower heads in the larger European markets; a water saving claim needs its flow and test pressure stated |
| The one mandatory scheme to plan early | WaterMark certification plus WELS registration for Australia, which belongs in the first RFQ conversation; confirm the New Zealand route separately |
| Factory reference conditions | Flow tested at 0.3MPa for selected specifications; pre-packing water test normally run at 0.5MPa as the leak point check |
Read the Thread, Not the Country
A thread designation carries three facts: nominal size, thread form, and whether the thread is parallel or tapered. G1/2 is parallel, from the BSPP family defined in ISO 228-1, with 14 threads per inch and a major diameter of 20.955 mm. It does not seal on the threads: the cone nut seats into the head inlet, and the hex nut compresses a washer against the mixer outlet.
1/2 inch NPT is tapered, and the taper is the point: the flanks interfere as the joint tightens, so the seal is made on the threads with tape or sealant. G1/2 and NPT share a nominal size and nothing else.
Japanese naming causes the most confusion on a first order. Current Japanese products commonly carry G1/2 at the hose connection. Japanese faucet documentation also uses the designation PJ, as in PJ1/2; LIXIL states that its shower connection is G1/2 and treats PJ1/2 as a compatible, equivalent designation, so it is not a tapered thread. Some mixers use maker specific threads, such as M22 x 2 on KVK fittings, W23 with 14 threads on MYM fittings and W24 with 20 threads on TOTO thick-hose mixers. Pack an adapter set and confirm against the actual faucet model.
| Connection | Thread form | Where it is native or used | Sealing and dimensions |
|---|---|---|---|
| G1/2 (BSPP, ISO 228) | Parallel | Europe, the UK, most of Asia, Oceania, Africa and Latin America; hand showers and hoses almost everywhere | Seals on a rubber washer at the mixer end and a cone face at the head end; 14 threads per inch, major diameter 20.955 mm |
| 1/2 inch NPT | Tapered | United States, Canada and Mexico shower arms; Gulf projects specified to United States standards | Seals on thread interference with tape or sealant; nominal 1/2 inch, not interchangeable with G1/2 |
| PJ1/2 (Japanese faucet documentation) | Parallel; treated by Japanese makers such as LIXIL as compatible with G1/2 | Japanese faucet and shower connections, alongside G1/2 on current products | Confirm against the faucet model; KVK, MYM and TOTO thick-hose fittings use M22 x 2, W23 and W24 threads that need an adapter |
| ZHONGHE adapter set (S, G, K, M) | Metric parallel on the fitting side, G1/2 on the head side | Legacy and non standard fittings in any market | S = M22.1 x 1.5, G = M21.3 x 1.5, K = M21.5 x 2, M = M22.1 x 1.75 |
Thread by Market
The table below sorts markets by what the wall gives you and what the hand shower gives you. Almost everywhere the hand shower and the hose are G1/2, and the only real question is what happens at the wall.
Two rows repay a second look. Mexico follows United States practice at the arm while using G1/2 on hand showers and hoses. Colombia and the Philippines can carry both conventions in the same housing stock, so the conversion point is set per order.
| Market | Wall outlet or shower arm | Hand shower and hose | Conversion point |
|---|---|---|---|
| United States and Canada | 1/2 inch NPT tapered on shower arms | G1/2 | Hose supply end or an adapter |
| Mexico | 1/2 inch NPT tapered, following United States practice; NOM-008-CONAGUA-1998 requires an NPT-compatible shower connection | G1/2 | Hose supply end or an adapter |
| United Kingdom | 1/2 inch BSP, the same parallel thread as G1/2 | G1/2 | None needed; check the riser rail diameter for slide holders |
| Germany, France, Spain, Italy, Netherlands, Poland | G1/2 (BSPP, ISO 228) at the mixer outlet | G1/2 | None needed; check the riser rail diameter for slide holders |
| Russia and Turkey | G1/2, written as half an inch in local catalogs | G1/2 | None needed; check the riser rail diameter for slide holders |
| United Arab Emirates and Saudi Arabia | G1/2 usually; 1/2 inch NPT on projects specified to United States standards | G1/2 | State whether the order is retail or project |
| India, Nigeria, South Africa, Australia | 1/2 inch BSP or G1/2 | G1/2 | None normally needed; S, G, K and M cover legacy fittings |
| Japan | G1/2 on current products; maker specific fittings on older faucets | G1/2 | Adapter set normally packed with the head |
| South Korea | G1/2 | G1/2 | S, G, K and M for older apartment fittings |
| Vietnam, Thailand, Indonesia, Malaysia and Singapore | G1/2 (BSPP) | G1/2 | Confirm the heater outlet where the head connects to a wall heater |
| Brazil, Chile, Argentina | 1/2 inch connections | G1/2 | Confirm the wall fitting with the importer |
| Colombia and the Philippines | Both NPT tapered and BSP parallel in use | G1/2 shipped by default | Conversion point specified per order |
Flow Limits and Labels by Market
A flow limit is a legal ceiling. A flow label is a marketing permission with rules attached. Confusing the two is the most common mistake here, because a product can be entirely legal and still be unable to carry the label a retailer wants on the box.
Numbers only mean something with a pressure attached. ZHONGHE flow tests selected specifications at 0.3MPa (3 bar, about 43.5 psi), where water saving specifications have measured roughly 50 to 70 percent below comparable non water saving heads. Where a market rule names its own reference pressure, that is the condition the compliance figure has to be produced at.
Every row below is an orientation reference, not a legal opinion. Confirm the current requirement with your compliance adviser or customs broker before artwork is printed.
| Market | Mandatory flow rule | Label or scheme | Practical note |
|---|---|---|---|
| United States | A federal maximum of 2.5 gpm at 80 psi commonly applies; the Department of Energy's 2021 showerhead definition was repealed with effect from 15 May 2025 | EPA WaterSense, voluntary, at 2.0 gpm or less (specification version 1.1) | California applies 1.8 gpm at 80 psi under Title 20, with all nozzles of a multi-nozzle showerhead counted together; confirm the current state rule |
| Canada | The National Plumbing Code of Canada (2020 and 2025 editions) requires individual shower heads to limit flow to 7.6 L/min, about 2.0 gpm | The model code is adopted province by province, with local amendments | Confirm the code edition in force in the destination province before setting the flow target |
| Mexico | NOM-008-CONAGUA-1998 sets flow limits by pressure class, with 4 to 10 L/min in its table and 2 to 10 L/min for hand showers; adjustable heads must comply in every setting | NOM conformity verified by accredited bodies | State the target flow together with the pressure it must be met at |
| United Kingdom | No single national flow ceiling applies to shower heads | The Water Fittings Regulations govern the fitting itself | Gravity systems can run near 0.1MPa, so specify a flow at a stated pressure |
| Germany, France, Spain, Italy, Netherlands, Poland | No single national flow ceiling applies | Voluntary water labels and retailer criteria apply only where a label or claim is used | State the flow with its test pressure, and check any regional or municipal water saving rule before launch |
| Australia | WELS registration and labelling apply to showers sold in Australia | Star rating driven by flow in litres per minute | The band boundaries are set by the scheme; confirm the current band table before a star goes on artwork, and confirm the New Zealand rule separately |
| Singapore | PUB, the national water agency, runs the Water Efficiency Labelling Scheme with mandatory and voluntary tiers | Check which tier currently covers showerheads before a label goes on artwork | Confirm the current scope with PUB or your importer |
| Japan | No mandatory maximum is commonly applied | 節水 is a headline retail claim | JIS standards cover faucet fittings and are commonly referenced for method rather than as a flow ceiling; confirm the applicable reference |
| South Korea | No mandatory maximum is commonly applied | 절수 is a recognised selling point | The figure has to be stated with its test conditions |
| Saudi Arabia and United Arab Emirates | Water efficiency rules and labels exist for sanitary fittings; whether a given shower head is in scope, and at what limit, is confirmed per product | SABER against SASO requirements; ECAS in the Emirates | Confirm the current limit and label format with your conformity assessment body before artwork |
| India, Brazil, South Africa, Nigeria, Vietnam, Thailand, Indonesia, Philippines | No mandatory shower flow maximum is commonly applied | No efficiency label is usually required | Tank fed supply makes low pressure performance the real constraint rather than the ceiling |
Water Fitting Schemes by Country
Schemes are granted for a product to an applicant, normally the brand or the importer, and not to a factory in general. ZHONGHE supports an application with samples, drawings and bills of materials, supplies component test reports, and arranges third party testing per project; certified options are available on request.
One entry differs in kind. WaterMark is mandatory in Australia for the plumbing and drainage products it covers, so it belongs in the first RFQ conversation; New Zealand has its own building rules, so confirm that route separately. For North American programs, the US and Canada importer page sets out the NPT and flow points together. Everything else is either a wetted material question answered by the bill of materials, or an import route the importer runs.
| Market | Scheme or route | What it covers |
|---|---|---|
| United States | NSF/ANSI 61 and 372; cUPC or IAPMO listing; California Proposition 65 | Wetted materials and lead content; wholesaler and code listings; a warning duty on the party placing the product on the market |
| Canada | CSA B125.1 and ASME A112.18.1; cUPC or CSA listing | Referenced by the National Plumbing Code; bilingual English and French labelling is commonly required |
| United Kingdom | WRAS approval or an equivalent Regulation 4 route; BS EN 1112 and BS EN 1113 | Water fittings connected to the supply; shower outlets and hoses |
| Germany, Austria, Switzerland | DVGW, with ÖVGW in Austria and SVGW in Switzerland; KIWA as a further route; UBA material recommendations | Drinking water fittings and wetted materials |
| France | ACS, the attestation de conformité sanitaire; the NF mark as a voluntary route | Materials in contact with drinking water |
| Netherlands and Belgium | Kiwa and Belgaqua | Products in contact with drinking water |
| Spain | AENOR against UNE-EN 1112 and UNE-EN 1113, voluntary | Product conformity; the Código Técnico de la Edificación governs installation |
| Italy | UNI EN 1112 and UNI EN 1113, plus national rules on materials in contact with drinking water | Shower outlets, hoses and wetted parts |
| Poland | A hygienic attestation from the national public health institute; PN-EN 1112 and 1113 | Products in contact with drinking water |
| Russia and the Eurasian Economic Union | EAC mark on a declaration or certificate; GOST standards referenced | Sanitary products across Russia, Belarus, Kazakhstan, Armenia and Kyrgyzstan |
| Turkey | TSE mark or TS EN 1112 and TS EN 1113 test evidence | Distributor and public tender requirements; imports screened at customs |
| United Arab Emirates | ECAS, with the Emirates Quality Mark as the higher tier | Regulated products; municipality approval can apply on building projects |
| Saudi Arabia | SASO requirements shown through the SABER platform | A product certificate of conformity, then a shipment certificate issued before arrival |
| Australia | WaterMark certification plus WELS registration | Plumbing and drainage products installed in Australia; the flow label. Confirm the New Zealand route separately |
| India | BIS, the ISI mark and Quality Control Orders | A widening list of goods; confirm current coverage for your tariff line |
| Brazil | INMETRO conformity schemes | Compulsory programmes focus on electrical products such as the chuveiro elétrico |
| Mexico | NOM conformity; NOM-050-SCFI | Commercial information on the label in Spanish |
| Japan | JIS standards and the Water Supply Act framework | Faucet fittings; leaching test methods for wetted materials |
| South Korea | KC certification; the Water Supply Act hygiene safety standard route | Designated product categories and waterworks materials |
| Malaysia and Singapore | SIRIM and SPAN; the Singapore water utility approves water fittings | Fittings used in the reticulation system; in Singapore, the WELS label where the product is in scope |
| Indonesia, Thailand, Vietnam, Philippines | SNI and SPPT SNI; TISI; TCVN and QCVN; the BPS PS mark and Import Commodity Clearance | National standards routes, mandatory for listed product groups |
| Nigeria, South Africa, Egypt | SONCAP with Form M and PAAR; SABS and SANS with JASWIC listing; importer or brand registration with the national import authority | Pre shipment certification and listings for water fittings |
What to Put in the RFQ
Seven lines turn this reference into a buildable specification, and each changes the tooling, the bill of materials or the artwork.
- Name the wall fitting rather than the country: shower arm thread, mixer outlet thread, and whether the head screws directly to the wall.
- State the thread for each end of every item in the order, since a head, a hose and a holder can each carry a different one.
- Give a target flow with the pressure it must be met at, and name the reference condition your market rule uses.
- Say which label the product must be able to carry, because a label criterion is usually stricter than the legal ceiling underneath it.
- Name the scheme the destination requires and who will hold the approval, since it is granted to an applicant rather than to a factory.
- Decide which adapters ship in the box, and write the compatibility statement that will appear on the packaging.
- Confirm every rule quoted here with your own compliance adviser or customs broker before artwork goes to print, then send the list with a model photo through the RFQ page so the thread, flow target and adapter set are quoted together.
Sources and official references
Official pages for the standards and rules named above; requirements change, so confirm the current edition with the certifying body before ordering.
- ISO 228-1: ISO standard for G parallel pipe threads (BSPP)
- 10 CFR 430.32: US federal water-use standards; showerheads are paragraph (p)
- Repeal of the Definition of Showerhead (90 FR 15647): US Department of Energy final rule, effective 15 May 2025
- EPA WaterSense: Showerheads: EPA's voluntary label for water-efficient showerheads
- NOM-008-CONAGUA-1998: Mexico's official showerhead standard (Ministry of Economy catalogue)
- National Plumbing Code of Canada 2025: Table 2.2.10.6: shower heads limited to 7.6 L/min (National Research Council Canada)
- ASME A112.18.1/CSA B125.1: North American standard for plumbing supply fittings (CSA Group)
- The Water Supply (Water Fittings) Regulations 1999: water fittings rules for England and Wales
- WRAS Product Approvals: UK approval scheme for water fittings and materials
- BS EN 1112: European standard for shower outlets (BSI)
- WaterMark Certification Scheme: Australia's mandatory plumbing product certification
- Water Efficiency Labelling and Standards (WELS) scheme: Australia's water efficiency labelling scheme
