Waterco Trimline MkIII Cartridge Filter Half Union - 40/50mm - 122257BLK

Waterco Trimline MkIII Half Union - 40/50mm

Genuine Waterco half union, part number 122257BLK, in black. This is the barrel union that connects the filter inlet or outlet to your pipework, supplied as the half union assembly. It takes either 40mm or 50mm pipe, so one part covers both plumbing sizes.

This is the post-2001 MkIII union. Replace it when the union nut has cracked, when the thread is stripped, or when the union weeps and a new o-ring has not fixed it.

Specifications

Part Number	122257BLK
Manufacturer Description	40/50mm Half Union MK3 (post-2001)
Pipe Size	40mm or 50mm
Colour	Black
Brand	Waterco
Quantity Per Filter	2 — one inlet, one outlet

Fits

Waterco Trimline MkIII cartridge filters manufactured from 2001 onward — C25, C50, C75, CC50, CC75, CC100.

The C100 and CC150 use a 40mm half union, part number 122243B. Pre-2001 MkII filters use a different union again, with union o-ring 620341. If you are not certain which you have, send us a photo of the existing union before ordering.

Fitting

A filter has two unions, inlet and outlet. If one has failed the other is usually the same age, so it is worth replacing both while the system is drained down rather than doing the job twice. Hand-tighten the union nut only — these seal on the o-ring face, not on thread tension, and overtightening cracks the nut.

Related Trimline Parts

• 122243B — 40mm half union, C100 and CC150
• 620341 — Union o-ring, 40/50mm MkII
• 620342 — Half union o-ring, BS332 Viton
• 62026 — MkIII lid o-ring, 214mm

---

Manufacturer Manuals, Diagrams & Part Numbers

Need exploded views, spare part numbers, diagrams, or more product information? See Waterco's Trimline Cartridge Filter manual.

Important Before Ordering: Please ensure you order correctly. Confirm this product is suitable before ordering. Use the manual above, seek professional assistance, or contact us with photos of your existing part, model details, serial numbers, and any labels.

As with all products, these must be diagnosed and fitted by a qualified and experienced person.

---