Lift the lid and check the accessories beneath it, something you can take care of yourself may need to be adjusted or replaced - flush the toilet and watch what happens.

When the tank is full add a few drops of food coloring to the water in the tank.

Come back in a while and see if the color is in the toilet bowl.

If it is you need to clean the flapper valve seat and replace the flapper with EXACTLY the same on that's in there. Use the scrubbie side of a wet kitchen sponge to clean the flapper valve seat in a circular motion

justalurker, I will drop some food coloring in tank. But if it is the flapper would it cause the pipes banging noise?

One thing at a time... otherwise you don;t know what solved which problem.

The toilet running can be the flapper. Check that and replace if necessary.

The pipes banging can be the float/shut-off.

In either case, these are easy repairs that you can do for a few bucks. Or you can choose to pay a plumber a lot...

I'm glad I posted. I definitely don't want to pay a plumber.

catie-
Once you get the problem figured out, feel free to re-post for info on how to proceed, if you need it.

Put food coloring in tank and there is no color in toilet. What else should I do. Thanks for the help everyone.

Make sure that the water level in the tank is BELOW the top of the overflow tube.

Make sure that the small tube that goes from the float assembly to the overflow tube is directed INTO the overflow tube but is fixed ABOVE the lip of the overflow tube.

I'm glad I posted. I definitely don't want to pay a plumber.

Checked water level and overflow tube, everything looks good, according to what justalurker posted. This is a mystery.

Checked water level and overflow tube, everything looks good, according to what justalurker posted. This is a mystery.

Without being there to actually see what's going on... that's all I got.

You have to pay a pro when you either don't want to do it your self or can't do it yourself... consider the cost tuition.

Is this problem a continuing one? Is there a chain to the flapper that might have a kink in it?

kudzu9, problem just started a couple of nights ago. Chain to flapper looks ok too. What's baffling me is the pipes banging when the water all of a sudden starts to run and then goes off on its own. Oh and last night I shut off the water to the toilet and no pipes banging and of course no water running. Guess I have to pay for a plumber.

Pipes banging can be caused by any valve opening or closing rapidly. Called hammering. More than likely the fill valve.

Since you haven't posted what brand, model, and style of toilet or any pictures it's hard for us to see what's going on.

Might not need a plumber. A competent handyman/woman should be able to solve the problem.

catie-
One other thought. Does your house have a pressure reduction valve installed? They are typically located right by the main shutoff valve. When those get old there is a diaphragm inside that starts to go and you can get chattering and weird noises.

Here is a link that might be useful: PRV

We don't have a PRV. Toilet is Toto Ultramax II. I'll take a closer look at the fill valve. Thanks for all the help.

The fill valve for the Ultramax II is part# TSU51A. For the most part, Toto has bought their fill valves from other suppliers. I have not repaired any of the Ultramax II 1.23 and have not determined who manufactured that particular fill valve. The TSU51A does not look like any of the present-day Korky offerings.
What I do know is that ordering the original Toto part number is rather expensive. For the original Ultramax 1.6, the flush valve is really a Korky 528 which Lowes sells for a bit less than $9.00. Buying the Toto part is over $25.00. Some of the same patent numbers are on both valves.
I too suspect the fill valve as the culprit. It is possible that the Korky 528 will fit your toilet-- it will cost you less than $10.00 to find out.
Look at line 1 on the parts list for substitutions and interchanges shown.

Here is a link that might be useful: Parts

There are probably not less than a thousand YouTube vids on how to do this. Go for it, Catie. Unless it is in fact a leaky flapper valve, which is also a simple fix.
When water moving through a pipe is suddenly stopped, as when a valve closes suddenly, the energy of the moving mass of water doesn't just vanish. If the pipe system has no cushioning device or design to absorb it, it manifests as a pressure spike that causes banging. Metal [copper or galvanized] pipes inadequately secured inside walls, so that they can move some, magnify and carry the banging through the house. Washing machine and dishwashers can also cause this, because they use solenoid valves that go from full open to closed in a fraction of a second.
Modern plumbing systems should be equipped with devices that absorb the pressure spike and prevent pipe banging.

Let's face it - there aren't many parts in the toilet tank. It isn't a leaky flapper so I changed the fill valve.

bus_driver, thanks, I found a Korky in Lowes.

airqual_guy I found a vid on YouTube that was very helpful.

Thanks everyone for the help. Keeping my fingers crossed.

It's totally easy...I've done it 4-5 times in my life and I'm useless and can't do anything handy :)

It even makes sense...so few parts involved.

Catie-
The standard Korky Is supposed to work well with every toilet, but they have a special (more expensive) model for Toto. The standard Korky functions in the Toto, but the fill level in the bowl doesn't get quite as high as it's supposed to. But it won't hurt anything. I know because I have three Toto Ultramax toilets.

The Korky 528 instructions include the height setting procedure.

Searching the internet turns up a number of complaints about the Korky. But it is obvious that not every user installed it correctly. I have not personally experienced any unusual problems with the Korky although I usually use Fluidmaster. The Ultramax is, in my opinion, cramped for space in the area of the flush trip lever and the Korky sits low and under the lever. That and low cost (to Toto) could have been the reason that Toto selected that unit.

This post was edited by bus_driver on Mon, Nov 10, 14 at 8:53

bus_driver- The height setting procedure adjusts the fill level in the tank, but it is not possible to adjust the fill level in the bowl.

Agreed. The design of the bowl and trapway limit the maximum height in the bowl, but the regular 528 fill valve could possibly leave it a bit too low. Lowes also has the 528T and the 528 MP.

This post was edited by bus_driver on Mon, Nov 10, 14 at 21:15

It's been about a week since I replaced the fill valve and up until now I haven't heard any pipes knocking. Yesterday all of a sudden pipes start knocking and I check the other toilet and it was making a hissing noise and the toilet wasn't even flushed recently. What are the chances that 2 fill valves have to be replaced.

I'm wondering if I should drain the system...?? Would that help? My fear is that I will have to call a plumber and he will rip open the walls. I have nightmares and sleepless nights over this thought.

Your other toilet is a ???. Same age as the first one? Forget the panic and think clearly.

The other toilet is the same, Toto Ultramax. Both are 7 years old.

Assuming that each is used about the same amount, simultaneous failures is not out of the ordinary.
My local Lowes does not have the 528T in stock but they do have the 528MP which has adjustable bowl fill. If the regular 528 is satisfactory for you, it might save a few ounces of water per flush. Home Depot might have the 528T.

Thank you bus_driver. This morning lifted the lid when I heard knocking noise and the water was running in the tank. When knocking stopped, water stopped. And the toilet was not used or flushed, it just happens all of a sudden.

I will change the fill valve in the other toilet as well. Keeping my fingers crossed this solves the problem.

Based on your latest post, there may be additional issues with your toilet. But do replace the fill valve to eliminate one of the possibilities.
Watch the video also.

Here is a link that might be useful: Youtube