Turn off the water at the shutoff valve behind the toilet by turning the handle clockwise. Wait 30 seconds. If the toilet drains into the bowl on its own, the flapper is leaking and water is escaping into the bowl. If the tank keeps filling, the fill valve is broken.
Remove the tank lid and set it somewhere safe. Look at the rubber flapper at the bottom of the tank. If it looks warped, cracked, or has mineral buildup around it, that's your problem. The flapper won't seal tight anymore and water leaks into the bowl constantly.
A toilet with a weak flush might be clogged. Use a plunger and push hard, making a tight seal around the drain. Push down and pull up fast, repeat 10 times. If water drains after plunging, the clog cleared. If it's still weak, the issue is in the fill valve or bowl design, not a blockage.
If you didn't see a cracked flapper or debris in the tank, turn the water back on. The problem might be the fill valve failing. A plumber can test it and replace either part in minutes. Most repairs take 30 to 45 minutes.
A toilet that runs constantly wastes water and makes your water bill climb. The culprit is almost always the flapper, a rubber piece at the bottom of the tank that lifts when you flush and seals when the tank refills. After years of lifting and closing, the rubber gets hard and warped from minerals in our water and from the chlorine used in local systems. It won't seal tight anymore, so water trickles into the bowl all day. The tank refills to compensate, so you hear the fill valve running constantly. A weak flush is different: the flapper is sealing fine, but there's not enough water in the tank to push waste down the drain fast enough. This usually means the fill valve isn't letting the tank fill completely, or the bowl has a silent leak that drains the tank slowly.
When a plumber checks a running or weak-flushing toilet, they look at the fill valve first to make sure the tank is filling all the way. They check the flapper for cracks and mineral deposits, and they check the bowl for cracks or slow leaks. Most of the time it's the flapper, and replacing it takes 10 minutes. A fill valve replacement takes a bit longer but is still straightforward. Both parts cost very little compared to wasting water for months.
A running toilet is not an emergency, but it's wasteful and annoying, and it gets worse over time. A weak flush can lead to clogs because not enough water is moving waste out. The longer you let either problem run, the more you waste water and the harder the flapper gets as minerals cake onto it. Homes in and around Seaside often have hard water, which speeds up mineral buildup on toilet parts. If your toilet has been running for more than a few days, a plumber can fix it in one visit.
Describe what you're seeing to a real Seaside plumber: call (831) 555-0140 or send the form. Free, no obligation.