Okay, you've replaced your old tank's worn-out flapper to stop the water from running. You've even pulled the whole thing out to fix a clog after your kid "accidentally" flushed a hairbrush. But you're still squandering water. Toilets made before the 1930s, with their period looks and their satisfying whoosh, can use as much as 6 gallons per flush. To preserve aging sewage systems and cope with regional water shortages, federal law now requires new toilets to gulp no more than 1.6 gallons. Rather than buy a new low-flow model, save yourself $200 or more by swapping out the mechanisms in your old toilet with the water-conserving ones in a universal repair kit, sold at hardware stores for about $20.