Crane, American Standard are decent brands

home depot or lowes

I have the very same problem with my Crane Plumbing toilet. Not every thing gets flushed down and can take 1 to 5 flushes to empty. Crane is the cheap brand that builders use. The one in your home is most likely (like mine) the $80 builders line. I found this out when I paid a visit to Home Depot. The resident toilet expert there told me all about toilets. It could also be a blockage or build up in the plumbing.

You may also consider a "ADA Toilet Spacer" which will give you the flexibility to use your existing equipment, but there are several companies that offer you a new toilet, if you wish. The major companies... i.e. Kohler, American Standard, Crane, Acorn etc. all have 18".

Yes. My parents had 2 out of the 3 Crane toilet tanks in our house break. One broke while we were gone for the weekend and it flooded our house because it kept trying to refill itself.

Crane recognized that there's a defect in the tanks from toilets from the mid 80s. However, they never did a recall on them. Instead they wait until the tank breaks and they'll replace the tank if you contact them.