Article Introduction
Here’s a trap that catches buyers every week: “4-inch” and “110mm” are NOT the same pipe. A 4″ NPS PVC pipe measures 4.500″ (114.3mm) outside diameter and follows ASTM D1785; a 110mm pipe measures 110mm (4.33″) and follows GB/T 5836.1 — they only look similar in photos. This guide covers 4″ PVC elbow dimensions, the real differences vs 110mm fittings, and how to order so the fitting actually fits.
How to measure pipe wall thickness
4″ and 110mm are two different standards, not two names for one pipe — 4″ NPS has a 4.500″ (114.3mm) OD; 110mm metric has a 110mm (4.33″) OD. They are close, but not interchangeable, and a 4″ fitting will not seal on a 110mm pipe.. They all talk about outer diameter, because this is matched with PVC fittings. Therefore, the diameter of the tube is unable to determine the thickness of the wall because it is the same. If you want to know the thickness of the pipe wall, simply take a vernier caliper to measure directly, or the diameter of the pipe minus the size of the aperture, and then divide it by 2 to get the result.
4″ vs 110mm: Side-by-Side
| Dimension | 4″ NPS (imperial) | 110mm (metric) |
|---|---|---|
| Outside diameter | 4.500″ (114.3mm) | 110mm (4.33″) |
| Typical wall (pressure) | 0.237″ / 6.02mm (Sch 40, ASTM D1785) | — |
| Typical wall (drainage) | 0.237″ / 6.02mm (Sch 40 DWV) | 3.2mm (GB/T 5836.1) |
| Fitting standard | ASTM D2466 (Sch 40) / D2467 (Sch 80) | GB/T 5836.2 |
| Markets | North America, export ASTM specs | China, parts of Asia, metric codes |
Read the imprint on the pipe before you order — “4\”” or “DN100/114.3” means ASTM; “110” printed alone usually means GB metric. When in doubt, measure the OD with a caliper: 114.3mm = 4-inch system; 110mm = metric system.
Connecting PVC Fittings to Other Pipe Materials
PVC fittings meet steel or cast-iron pipe most often through flanged joints on medium and large diameters — bolt up a PVC flange to a steel flange with a gasket and you’re done. On smaller sizes, use adapters or unions: a socket adapter glued to the PVC side, a threaded adapter or male/female thread connection on the metal side. Mixing thread types is a common mistake — always match the thread standard (NPT on export lines, BSP on metric systems).
Common angles and specifications of PVC pipe elbows
Angles
Three angles cover almost every job: 45°, 90°, and 180° (U-bend). The 90° is the workhorse; the 45° is for gentle transitions and drainage branches; the 180° return is for trap arms and drain loops.
Specifications
In the imperial system, 4″ elbows are made to ASTM D2466 (Schedule 40) or D2467 (Schedule 80) with a 4.500″ socket bore to match 4″ pipe. In the metric system, the equivalent is 110mm to GB/T 5836.2. Other common metric sizes: 32, 40, 50, 75, 90, 110, 125, 160, 200, 250, 315mm. Pipe is generally supplied in 4m or 6m lengths; anything else is negotiated between supplier and buyer.
How to choose the size of PVC elbow
The size of the PVC elbow depends mainly on the diameter of the connected PVC drain pipe. Common PVC elbow sizes include 32mm, 40mm, 50mm, 75mm, 90mm, 110mm, 125mm, 160mm and 200mm, etc.
When choosing an elbow, you need to pay attention to the following points:
Matching pipe diameter: The diameter of the elbow should match the diameter of the connected drain pipe. For example, if the diameter of the drain pipe is 50mm, a 50mm elbow should be selected.
Bending radius: The bending radius of a 90-degree elbow is usually 1.5 times the diameter of the pipe. Depending on specific needs, long radius or short radius elbows can be selected.
Material and brand: Choose a well-known brand of PVC elbow to ensure that the material is environmentally friendly and has no irritating odor. High-quality PVC elbows usually have no odor and a smooth and uniform appearance. For example, SAM-UK is a high-quality pipe supplier.
Application and pressure: match the fitting class to the system. Schedule 40 for general drainage and supply up to 140°F (60°C); Schedule 80 where pressure or abuse is higher; for hot water, move to CPVC (200°F / 93°C) — PVC itself is not a hot-water material, and no “seamless” or alloy version changes that.
Through the above points, you can ensure that you choose the appropriate PVC elbow size to meet different usage requirements.
Summarize
Order by system, not by name: a 4″ elbow is ASTM-sized (4.500″ / 114.3mm OD) and a 110mm elbow is metric (110mm / 4.33″ OD). Read the imprint, measure the OD with a caliper, and specify the standard on the RFQ — ASTM D2466 for 4″ Sch 40, GB/T 5836.2 for 110mm. Get the system right and the fitting is a non-issue; get it wrong and nothing seals.
SAM-UK supplies 4″ PVC elbows to ASTM D2466/D2467 and 110mm fittings to GB standards, with NSF certification — browse the 90° elbow range or contact our team for drawings and lead times.
Frequently Asked Questions
1. Is a 4-inch PVC elbow the same as a 110mm elbow?
No. A 4″ elbow has a 4.500″ (114.3mm) socket and follows ASTM D2466; a 110mm elbow has a 110mm (4.33″) socket and follows GB/T 5836.2. They look similar and don’t seal on each other’s pipe.
2. What is the wall thickness of 4″ PVC pipe?
Schedule 40: 0.237″ (6.02mm); Schedule 80: 0.337″ (8.56mm), both to ASTM D1785, on a 4.500″ outside diameter. A 110mm GB drainage pipe is typically 3.2mm wall — that’s a different product in a different system.
3. How do I measure an elbow to check the size?
Measure the inside diameter of the socket with a caliper — 4.5″ means 4-inch system, 110mm means metric. Wall thickness: (OD − ID) ÷ 2, or measure directly with a caliper.
4. Can I use a 4″ fitting on 110mm pipe?
No. The 0.17″ (4.3mm) OD difference is enough that solvent joints won’t seal and pressure joints will leak. Use the fitting that matches the pipe’s imprint and measured OD.
About SAM-UK
SAM-UK are a professional 20+ years manufacturer in producing vinyl building profile products and PVC , CPVC , PPH , PPR , PP pipes and pipe fittings, valves, taps and so on. We own the certificates of SGS\SONCAP\ISO9001\CE\NSF，support color /size customization. Welcome to consult for Catalog and Product. you can contact us at email [email protected]
