You're overthinking this way too much. Don't inject water into your body. If there is any bacteria in the water it could cause issues. Only inject sterile products that are made for being injected in your body. it truly is nothing to worry about. Take a shower right before so i softens your skin. Prepare everything and just do it. Don't worry about wasting gear. you won't. If you do inject and don't release the gear make sure to swap out the needle tip. Also be sure to change the needle once you inject into the vile.