FOR FLUSHING ISSUES
Turn off the water to the toilet, flush the toilet to minimize the water in the bowl, and pour in a gallon of vinegar to remove scale and mineral deposits. Leave the vinegar in the toilet for 24-48 hours. This may improve the flushing.
The goal is to open the ports in the toilet so the water moves more swiftly and therefore may flush better. The other possibility is that the porcelain is now worn to a less smooth surface and the toilet is ready to be replaced from hard water.
FOR TANK MAINTENANCE
Remove the top lid on the toilet and inspect the lever on the inside of the toilet tank. One option is to put a little vinegar, Lime Away bathroom cleaner or CLR on the inside of the trip lever. There is likely a build up of mineral deposits on the trip lever so a little cleaner might help. If the lever loosens up, then spray a little WD-40 on the lever pivot point.
Second option could be a lose nut on the inside of the lever that may need a little tightening. The nut would be about 1 inch in diameter and just tighten it up a little past finger tight.
If these solutions do not work then replace the whole toilet guts with a Fluidmaster replacement.
FOR GENERAL CLEANING & MAINTENANCE
The black lines in your toilet are algae growing in the mineral deposits on the porcelain inside your toilet bowl. Cleaning the algae with chlorine bleach lasts only a short time because the lime deposits hold the residue and moisture, which provides a nice culture for the algae to thrive.
The effective solution is to acid clean the porcelain to restore the smooth surface of the toilet. This was shared by a plumber on the show some months ago and he was adamant that it works without damage to the toilet.
Be careful … I believe that there are some cheaper toilets with absent porcelain or damaged finishes that can be harmed from this acid treatment so be careful to note any severe bubbling like a boiling that may occur from this acid. If you have this “boiling” problem just flush your toilet many, many times to dilute the acid in your toilet and your plumbing pipes with the water.
The process is to dip most of the water out of the toilet bowl and pour in two quarts of muriatic acid in the bowl or enough to cover the water line where the black marks occur in the bowl. Take the toilet brush and wash the edges under the top rim of the bowl several times with the acid. The acid will eat away the lime or mineral deposits and leave the porcelain unaffected. Apply several widths of cellophane like a Saran Wrap kitchen plastic over the toilet bowl to fully cover the toilet bowl and hold the fumes in the toilet and to minimize the hazardous fumes in the bathroom.
Let the acid sit in the toilet for about 15 minutes, remove the plastic cover and dispose it safely. Rinse the acid under the toilet rim one more time with the toilet brush, and then dispose the toilet brush safely. Then flush the toilet 10 to 20 times over the next hour to rinse and dilute the acid in your waste or drain pipes. Then clean the toilet in the typical way with normal house hold cleaners. According to the plumber your toilet should work well again and stay clean much longer than before the cleaning.
The acid is very nasty and creates acid fumes so protect yourself. Rubber gloves, good ventilation in the bathroom, long sleeves, and eye protection are required for your safety while working with the acid. Remember to flush your toilet many times after the acid flush.
Household Vinegar can be used instead of the acid. It’s not as strong as the acid, but is certainly safer.