My mate is building a home brewery, with two 240v pumps which he wants to control from a double gang splashproof lightswitch, fed from a 3 pin plug via a RCD. He’s asked me, which is not the best idea tbh.
The pumps just have 3 core mains cable. Question is, does the neutral have to be switched, or just the live? With the neutrals and earths connected separately. If he wires it like my diagram, will he die? The lightswitch doesn’t have COM, L1, L2 legends as I was expecting…

Edit – pics aren’t showing, will try to fix

Back of the lightswitch:

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Like this?

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That would be fine, if the switch is rated for the motor start up current.
Typical light switches are 10 amp maximum. Or, is it a double pole 20 amp switch?
What rating are the motors? Be aware, the start up current is typically double the running current, so switch gear should be sized accordingly. Thats why many motors are switched via a contactor.

Don’t remember the rating but nothing too heavy duty, less than an amp per pump or something.

Did he buy those 19LPM pumps that are on Ebay for ££80? perfect for home brewing , stainless business end and mag drive so no shaft seal to get glazed with wort.
As for wiring , a lighswitch with good IP rating should be OK , but for the HLT and kettle element I would use a sealed rotating isolator probably
The £10 set point controllers on Ebay also work well enough for commercial use so worth getting a box of 5 ( works out cheapest ) and having them permenatly fitted to each bit of kit