Debris that builds up over time inside the water system, including the valve body, supply line or shut off valve (at the wall) can restrict the flow path of water and slow down the valves filling speed. Toilet fill valves in use for a period of 7 years or more can have their working parts start to wear out.
Make sure the water shut-off is completely open for maximum water flow. If it's not completely open, that may account for your slow-fill issues. If you've tried the water supply and that isn't the issue, try cleaning the pump and valve. Sediment can build up over time, and a good cleaning may fix the issue.
Most likely your fill valve is getting old and is sticking when the level drops, so it shows up as a delay in that the float is not falling when it should. This would be an indicator that it is close to failing completely and needs to be fixed / replaced.
Adjust the fill valve
A) For older toilets: Loosen the adjustment screw and raise the fill valve. This should help put more water into the toilet tank. B) For newer toilets: Turn the fill valve adjustment knob by hand to let more water into the tank.
In general, a single flush 1.6 gpf or 1.28 gpf toilet tank will take around half minute (30 seconds) to one minute (60 seconds) to fill. Here are few steps to verify if your toilet tank takes longer than one minute to fill: Verify if the water supply valve is fully open.
If the fill valve appears to fill the tank slower than before, then debris has likely blocked the debris screen inside the valve. This will need to be flushed from the debris filter. Turn off the supply to the toilet. Remove the tank lid.
The toilet tank fill tube may be damaged or incorrectly positioned, preventing the water level from reaching its proper level. Position the fill tube so water is flowing into the overflow tube (the open pipe near the center of the tank). If this doesn't fix the problem, replace the fill tube.
After each flush, the fill valve controls the water flow into the toilet tank. This valve is regulated by a float, which acts as a signal to open the valve as the tank empties and closes it once it's refilled with water. During a flush, the water in the tank is depleted, causing the float to drop.
The problem is usually in the fill tank. If the water level in the tank is dropping, check the flapper. If it's not sealing the flush valve opening, water from the tank will leak into the bowl, and the toilet will run constantly to keep the tank filled. Replace the flapper as needed.
Perform a Dye Test
Add a few drops of food coloring into the toilet tank and wait for about 30 minutes without flushing. If you see the colored water seeping into the toilet bowl, your fill valve is likely the issue.
Check your water levels
Low water levels in your tank are common causes of toilets filling up with water when flushed. They can also cause slow-draining toilets. You can manually top up your tank with water to help the flush. Then, check the flush tube for cracks and bends that lead to leaks.
The main reason for a toilet tank not filling or filling slowly is due to the toilet fill valve. The most common reasons for the fill valve to slow down or no longer fill the tank after the flush are debris issues and the length of time a fill valve has been in use.
Locate the screw that attaches the float to the fill valve (usually on top of the fill valve). Using a screwdriver, turn the screw in small increments to adjust the water level. Clockwise will raise it and counterclockwise will lower it.
Water draining slowly – This means a partial blockage is forming that isn't big enough to block the toilet completely. The bowl remaining empty or almost empty – This indicates that there is a problem with air circulation in the waste pipes.
The different causes of this problem include a problem with the water supply line, a malfunctioning float ball, broken fill valve, clogged tank inlet holes, or a faulty flapper valve. These issues can cause inconvenience and affect the hygiene and sanitation standards of your home.
Heat 1 to 1 ½ cups of white vinegar to about the same temperature you'd take your coffee – not scalding, but warm enough. Add it to the overflow tube and give it about 30 minutes to work. Flush, then go to work on the jet holes, chipping away the scale with something small but solid.
Every time you flush, toilet tanks are supposed to refill with water. The water level should be about a half inch below the overflow tube and take around 10 seconds to refill.
If the tank is not filling with water, the float ball is not returning to the seat properly. Check to see if the linkage that connects to the trip lever is hung up. If that doesn't work, then the ball needs to be replaced. A flapper ball can replace a worn flush valve ball.