Look on the top of the rubber part of the 502 flapper. You will notice numbers 1–9 (Min–Max). The number that is located directly in front of the chain is what the flapper is set on. The lower the number it is set to, the quicker the flapper will close, allowing less water to flush out of the tank.
Adjust the Float: - Locate the float mechanism in the tank. If it's adjustable, lower the float to reduce the water level in the tank. This will decrease the amount of water used per flush.
You can elevate the ball float by turning the screw above the fill valve. Raising the float should raise the water level and hopefully solve your water pressure problem.
More water in the tank can contribute to a stronger flush. Flush Valve Size: The size of the flush valve, which controls the release of water from the tank into the bowl, can impact flush strength. A larger flush valve can allow more water to flow into the bowl quickly, creating a stronger flush.
Faulty Float Mechanism
The float controls the water level in the toilet tank. If the float is damaged, set too low, or obstructed, the tank won't refill with enough water to produce a powerful flush.
Look at the fill valve
You can also try adjusting the fill valve. Turn the adjustment screw of the fill valve to change the water level. You can check your toilet's instruction manual for help if you need it.
Here's how to address PRV issues: Locate the PRV, usually near the main water shut-off valve. Look for an adjustment screw on top of the valve. To increase pressure, turn the screw clockwise.
Even though high water pressure is not the top reason a toilet may be continually running, it can become a serious issue for the toilet and all the other plumbing fixtures if the water pressure exceeds 80 PSI.
Push the valve in the corresponding direction depending on what you need to adjust the flush. Adjust the ball valve to match the new height of the fill valve with a screwdriver. Twist the screw clockwise to raise it and counterclockwise to lower it.
Accumulated debris, waste, or foreign objects can obstruct the plumbing system, causing water flow restrictions and resulting in a hard-to-flush toilet handle. Similarly, a partially clogged or blocked trapway can impede the flow of waste and water, leading to inefficient emptying.
Shut-off Valve Location. If your toilet is produced or manufactured in America, you can usually find your shut-off valve on the back left side of the toilet.
Install a pressure-reducing valve
Installing a pressure-reducing valve can regulate and decrease the incoming water pressure to a safe and optimal level for your home. A PRV valve can lower water pressure coming into the home if the municipal water supply has a high pressure exceeding 80 PSI.
Flush less water down the toilet
There are easy ways to cut this by: installing a water displacement device (or 'Save-a-Flush') in the cistern of a higher flush toilet – these cut the amount of water used for each flush, typically by one or two litres.
Check the water level:
This cause by far the most common reason for slow flushing toilets. If the water in the tank is not up to the recommended level, you may have poor flushing power.
There is only one Drano® product recommended for use in slow-running toilets: Drano® Max Build-Up Remover. It contains microorganisms that break down organic matter in pipes that can slow water flow. (However, it will not open a completely clogged toilet. For that problem, see How to Unclog a Toilet.)
Check with your water supplier
It could be that the mains' water pressure has increased, which is an issue with your water network. Call your water company to see if they have set the pressure higher than normal because of maintenance work. You might also find that neighbouring homes have reported the same issue.
If the water pressure regulator is not adjusted properly, you could have either too much, or too little pressure in your faucet or shower. With the right tools, you will be able to adjust the water pressure regulator by yourself instead of calling in the plumber.
Adjust the Fill Valve: If the water level in the tank is too low, your toilet may not flush correctly. Adjust the fill valve to ensure the water level is about an inch below the overflow tube. Clear Clogs in the Flush Pathway: Use a plunger to dislodge any potential clogs in the toilet bowl.
Decide whether you need to raise or lower the water level. 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.
Restricted Water Supply Valve
When the water supply valve is partially closed or obstructed, it reduces the amount of water available for flushing, leading to turbulent flow and disruptive sounds like gurgling or splashing.