Water Tank Low on Water? Toilet Overflow Tube Broken or to Short? Overflow tube extension, By NuFlush. Add more water to your toilet tank and bowl. Flush more water one time and keep your toilet cleaner. The more water you can put into your toilet the better it will flush. Just replacing inlet and flush valves will probably not improve your toilets flushing power. Don't just fix your toilet. Change your toilet into a power flusher.