Toilets are, comparatively, simple mechanical devices. However, sometimes the fill valve that shuts off the water gets clogged (dirt, gravel, grit, etc.) and does not shut off when the float reaches the set height during filling. This causes the water to continue to run and fill the tank, though an overflow drain exists to prevent flooding. For one week, a toilet in your house has been running constantly because the fill valve does not close. Youve ignored it because life. Estimate the cost of the water usage over the week due to the toilet constantly running.