Drain screw for Preva, Winner, Mini and Micro Delfino pumps

Dimensions and basic details

The drain screw closes the opening used to drain water from the pump. It is removed when draining before maintenance or winterising. Compare the thread, height and shape with the original part; a matching pump name alone is not sufficient.

What the drain screw does

During operation, the screw closes the drain opening in the hydraulic section of the pump. Unscrewing it allows water to drain from the relevant chamber. Draining is important before dismantling the pump or preparing it for winter, for example. Follow the instructions for your model: opening a single drain may not fully drain the entire assembly.

Pumps for which this part is listed

• Preva 25, 33, 50, 75 and 100 – in the older diagram, the screw is at position 6 and the seal at position 7.
• Winner – older and newer versions listed in our spare parts guides. Check the original screw against the diagram for your pump.
• Micro Delfino 25, 33 and 50 – screw at position 69, seal at position 68.
• Mini Delfino 33, 50, 80 and 100 – screw at position 69, seal at position 68.
• Optima – compare the original part and dimensions before ordering; we can check the specific version using the pump identification.

The Micro and Mini diagrams show catalogue code B4180111. We use this existing product listing for these ranges. The gallery contains diagrams with an arrow to help identify the part.

When to replace the screw

• The original screw was lost during draining or maintenance.
• The head is damaged and the screw can no longer be reliably loosened or tightened.
• The screw has damaged threads or a visible crack.

If the thread in the pump housing itself is damaged, a new screw may not solve the problem. First assess the condition of the housing and the appropriate repair method.

Important points when replacing the part

1. Switch off the pump, disconnect the power supply and release the pressure according to the equipment instructions before opening. Secure the water supply to prevent uncontrolled drainage when the screw is removed.
2. Remove the original screw and inspect the seal. Remove dirt from the seating surface and thread.
3. Check that the new part matches the original. The screw must fit without force; do not tighten it against resistance.
4. Tighten according to the pump instructions. After restarting, check that no water leaks around the opening.

Remember to check the seal

The seal is also listed separately under code S92400035. If the original seal is damaged, make sure you have a replacement ready before installation. Separate 1/4″ drain screw seal →

Need help checking the correct part

Email info@chemie-bazen.cz with a photograph of the original screw, its dimensions and the pump identification. A photograph of the rating plate also helps. These details allow us to compare the appropriate version.

Spare parts guides

• Preva
• Winner older version
• Winner newer version
• Micro Delfino
• Mini Delfino