I have a watering system for my birds that is based on a 4" PVC pipe/reservoir, about 24" tall. Water usually lasts 4-7 days depending on weather. I've been trying to figure out a creative way to rig up an indicator so I know when the water level is getting low. I'm afraid I'm going to forget to check it for a couple days in a row and have a problem. I don't have a ton of room between the top of the reservoir and the coop roof, so a tall float won't work. Any suggestions?