Morning all, Our Bristan Java Thermostatic Shower has been leaking, we've replaced the cartridge but it was still leaking. On further inspection we found that the hot water piston was 'sticking' and would not compress and retract easily. We've bought the replacement pistons as well as the bristan maintenance tool to remove the pistons. This tool proved to be useless, as the pins fell out of the tool on first use. I've tried using some long nosed pliers to to turn the piston but it simply won't budge. I'm desperate for any advice on how to remove the piston. I've attached some images for reference. I'd be grateful for any help.