Toilet is very slow filling tank with water to flush

Toilet tank won't fill up or is slow to fill. The most common reasons for a valve to slow down or no longer fill the tank after the flush are debris issues and the length of time a valve has been in use. ... Valves in use for a period of 7 years or more can have their working parts start to wear out. 1.
https://www.fluidmaster.com/toilet-problems/remove-fill-valve-cap-replace-seal-toilet-wont-fill-slowly-filling-tank/

Usually there is a screan that is on the bottom of fill valve on the outside of tank were the water inlet is you can shut water off and remove srean and flush out if it dont have one you will have to remove the valve from tank and flush out in kitchen sink or faucet.

replace float assembly

Is the flapper valve slow to return to the closed postion allowing water to flow through the flush valve? Make sure the toilet flapper is moving freely and is sealing properly against the flush valve. If there is no lengthy or continual water flow in to the toilet bowl then this is not the problem.

Is the water valve on the water fill line to the toilet tank fully open? This may seem silly but it could be this simple.

Check to make sure your fill valve is opening fully. If you have an older toilet there may be some deposits that need to be cleaned way to allow free movement.

If toilet does eventually fill to the desired level, there is no leakage, water valve on fill line is fully open and fill valve is opening fully then recommend you shut off water supply, drain toilet and disconnect water fill line from the water valuve and toilet tanke to make sure there is not a blockage. If the water line and connections are clear you may need to remove the fill pipe in the tank and check for blockage. If this is very old, conisdering the cost and effort, it may be simpler to replace at this time rather than trying to extend the life.

I would suspect that the flush valve has a blokage in it that is causing a harmonic distortion to be transmitted thru your cold water piping.. One way you may be able to help this is to slow fill rate down on your flush valve. If your fush valve has a seperate float to shut off water supply to tank when it;s full there should be a adjustement screw onside of valve where float rod goes in. Adjust screw down to raise float and thus slow fill rate of tank, this should help with the noise. Ifyour toilet does not have adjustable float see if you have a valve on incoming water supply. If you do you can try slow down flow thru supply valve and see if that helps, Thanks

The amount of water in any toilet bowl is determined by its construction and no tank adjustment will ever change that. American Standard has a history of having small water surface areas in their low or ultra low flush toilets. Take a large container of water and pour directly into the bowl. If the ending level remains the same, then that is the manufactured level for your toilet.

Not all tanks completely discharge all of the water when flushed. Measure 1.5 gallons of water into a container. Turn off your water supply to the toilet then flush normally. Replace the water in the tank with your premeasured amount and observe this new water level. You might be surprised to find it is at the same level it always is. Since water weighs more than 8 pounds per gallon, one concept used in todays toilets is to have more than 1.5 gallons of water in the tank and use the extra weight push the water past the flapper at a faster rate while designing the flapper to drop after only 1.5 gallons have passed through.

if the toilet is old or not cleaned proper, the water jets that shoot the water into the bowl might be clogged. If the jets are clogged with moldor hard water build up the toilet will not flush proper. If you can take a 3 gallon bucket of water and pour straight into the bowl and it flushes fine you have a water pressure problem as described above. the problem also might be that your water inlet system is not letting in enough water to fill the tank. If this is the problem you need to replace the water inlet mechanisim, such as a fluid master. If you use a blue water device that hangs on the side of the tank in the back of the toilet you might have a peice of it under the flapper that takes the water to the bowl when being flushed. Check under the flapper if you put cleaners in the tank.

Okay Howard. It seems that the fill or float valve inside the toilet tank needs to be replaced. If you have a pair of channel locks / large pliers and some patience, you can do this yourself and save $ on a service call. This Solution is providing that you have good water pressure everywhere else in the house. First turn off the water on the supply line going to the tank. Flush the toilet (with the water off) to empty the tank. Take a towel / sponge / or wet vac to remove any remaining water. Remove the nut on the underside of the tank that holds the float / water supply to the tank. Now that you have the water float removed you can go to your local hardware store / Home Depot / or Plumbing Supplies Store and get a new fill valve. There are different kinds but they all do the same thing, fill your tank. I use a Fluid Master, But you may have to use one like you have. The Store will assist you. They are only about $10 - $15 Bucks or so.......Install the new float according to directions.....It is pretty simple. Insert your new float stem into the hole with the proper rubber washers and tighten carefully for a good seal. Insert the new black hose into the overflow tube and you are in business. You will have to adjust the water level to about a 1/4 Inch below the overflow tube for a good flush!!! I hope this helps you with the slow tank fill.............Joe

there are allot holes around rime inside they get clogged over time because water quality very hard to get there to clean best bet replace toilet