Drain valve for Astralpool ZX cartridge filter

I needed to rearrange the pump and filter setup of our above ground pool. The only problem with the new arrangement is that the drain-hole for the filter (Astralpool ZX100) points towards the pool wall instead of away from it. This side of the pool is on the shady side, and takes a long time to dry out, so I don’t want that area getting wet unnecessarily. So I investigated the possibility of replacing the drain plug with some kind of valve or tap, so I could drain the water away through a hose.

Astralpool ZX cartridge filter

The drain plug has two threaded sections and can be removed completely if unscrewed carefully. At first I thought the plug was anchored inside the filter housing so that the plug wouldn’t come free and get lost. But the ‘anchor’ is just a second threaded section. Be careful unscrewing or re-screwing the plug – it would be easy to cross-thread it.

It was difficult to find a suitable valve to replace the plug. The plug appeared to have a 1/4″ BSP thread. (But a lot of pool equipment is designed in or for the USA so there was a real possibility the thread was actually the US equivalent: NPT). This is pretty small so I was looking for a tiny valve. I wandered around Bunnings for some time without much success. I was looking for 1/4″ BSP male on one end and a barb on the other to attach a piece of hose. Actually at first I had many possibilities in mind, including some sort of bulkhead fitting for the inside of the filter case and a female threaded valve outside. I also thought of using a home brew kettle valve but they are expensive.

I couldn’t find what I wanted so I searched ebay and eventually found a 1/4″ BSP to barb brass ball valve. It was only $3 including postage from China. Designed for use in either pneumatic or hydraulic systems it should be able to handle 12-15 psi of slightly salty water.  It took a while to arrive from China but it fits perfectly. I thought I may need to use some teflon tape on the threads but so far the rubber o-ring from the plug is making a water-tight seal.

Brass ball valve and original plug

The new brass ball valve and the original ABS drain plug.

Ball valve with hose

I attached a piece of hose from an old washing machine. Ready to screw into the filter housing.

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