V0421 Quartz Sleeve O Ring for Wonder UV Units

The V0421 is a replacement O-ring used to seal the quartz sleeve assembly in Wonder UV disinfection units. Supplied by WrekinWater, it fits between the sleeve and the housing to keep the joint watertight where the sleeve passes through the end cap. It's a low-cost part worth renewing whenever you service the lamp or sleeve, since a perished or flattened O-ring is a common cause of a weeping joint.

Signs this O-ring needs replacing

• Weeping or dripping visible at the sleeve/end cap joint
• The rubber feels hard, cracked or perished when checked
• A drop in seal pressure after refitting the housing
• You're replacing the quartz sleeve and the old O-ring looks worn

The V0421 O-ring seals the point where the quartz sleeve passes through the end cap of a Wonder UV unit, stopping water from tracking along the sleeve and into the lamp chamber. Rubber perishes over time through a combination of age, water contact and warmth from the lamp, gradually losing the elasticity it needs to hold a watertight seal. A hardened or flattened O-ring is one of the most common causes of a weeping joint, so it's worth renewing whenever you service the sleeve or lamp.

WrekinWater is a family run business based in Bettisfield, Shropshire that has supplied water treatment parts to more than 50,000 customers over 15 years and holds an Excellent rating on Trustpilot. Keeping a spare V0421 on hand means a weeping joint can be fixed in minutes rather than waiting on a part.

How to replace it

1. Isolate the water supply to the Wonder UV unit and drain the housing
2. Undo the retaining nut or union to release the end cap
3. Withdraw the lamp and sleeve, then remove the old O-ring
4. Clean any residue from the O-ring groove
5. Lightly lubricate the new V0421 with food-safe silicone grease and fit it
6. Reassemble the housing, restore water and power, then check for leaks