The water tank is simply a no-counter to all criminals, it puts you on ground over and over again without having anything to counter it.
I`ve seen many times more than 2 water tanks in SR and guess what? its a simply no-play.
I would suggest having some kind of storage just like Nitros or just make it not allowed at SR as its a special vehicle(CLO/DE cant have anything special in SR, I dont really understand how that rule doesnt applies to cops)
You can also make it allowed ONLY if CLO is at SR?