DN40 Service Kit

This Greenlife DN40 service kit supplies the replacement seals for re-servicing a closed circuit magnetic filter housing fitted on DN40 (1 1/2in) heating pipework. WrekinWater stocks it for anyone carrying out the annual clean-out or resealing a housing that's started to weep. It's sized specifically for the mid-range Greenlife DN40 filter, so it won't suit the smaller DN20/DN32 or larger DN50/DN80 housings.

Signs you need this part

• Weeping or dripping visible around the DN40 housing joint under system pressure.
• Seals feel hard, glazed or flattened when the housing was last opened for cleaning.
• You're rebuilding the housing after removing the magnet bar for its annual clean.
• Persistent damp patches on the lagging or insulation directly around the filter.

On a DN40 closed circuit filter, the housing seals are the only thing standing between the pressurised heating loop and the outside of the unit once the body is reopened for cleaning. Constant heat cycling and the chemical inhibitors typical of closed systems dry out rubber seals faster than the plastic or metal housing around them ages, so seals that sealed fine a year ago often won't reseal reliably a second time. Replacing them at each service is a cheap way to avoid a slow leak developing weeks after the housing was last opened.

WrekinWater has been supplying water treatment parts from a family-run base in Bettisfield, Shropshire for 15 years, serving more than 50,000 customers and holding an Excellent rating on Trustpilot. Buying the DN40-specific kit here avoids the guesswork of using seals sized for a different Greenlife housing.

How to fit it

1. Isolate the heating system and allow it to cool before opening the housing.
2. Shut the isolation valves either side of the filter to remove pressure from that section.
3. Undo the union nut or clamp and separate the DN40 housing body from the head.
4. Take out the old seals and clean the sealing faces of any debris or scale.
5. Fit the new seals from the kit and reassemble, tightening the union hand-tight plus a quarter turn.
6. Reopen the isolation valves gradually and check the rebuilt joint for leaks before leaving it in service.