The maximum water level in the bowl is determined by the design of the bowl trap,,,there is no way to adjust it

Hi,A couple things come to mind.
One of those padded toilet seats may cure your problem.
Try removing the tube to the overflow in the tank. Your toilet may not flush right but it is an easy try.
Good Luck Woodbutcher

There is another alternative...although I hesitate to even mention it,,,Perhaps a doctor could do more to relieve this complaint than a plumber..on second thought , perhaps a veterinarian has even more expertise.

Ouch! Thanks, but no thanks Lazypup. "Lazypup?" Hmmmmmmm. Maybe you have been to that vet and ended up lazy?? No, but thanks for replies. If it were my house I would replace the toilet. An apartment? No. And if I did, the wife would decide it was time to find another place...again!

Actually I have the same complaint. In summer it is tolerable but in mid winter when you just crawled out of a nice warm bed that cold water is a bit of an unexpected eye opener

Actually, there is one way to make it lower. Slow down the refill level of the bowl by constricting the tube leading to the overflow tube. Adjust so that it just barely fills it to the level needed by the time the fill valve shuts off *when the tank is full). Trial and error to get it just right. I think the Fluidmaster fill valve with "leak sentry" comes with a plastic ring/screw that adjusts to slow the flow in this manner.

ABSOLUTELY DO NOT RESTRICT THE TRAP PRIMER LINE

If you restrict the trap primer and cause it to leave the bowl below its intended level that will leave the trap open for sewer gas to enter the structure.

LP, any idea how much lower the bowl water has to be to actually get an open trapway? It's got to be a lot lower than the "full" level under normal operation. Of course, flush performance would be affected adversely if it's too low, anyway.

I removed the refill line from the overflow tube on mine, there is still sufficient water in the trap and it solved my "spash" problem. Works fine for #1 but doesn't flush well for #2.

A proper complete flush requires approximately 2-1/4 to 2-1/2 gal to flood the trapway and begin the flushing action.

Years ago water closet tanks discharged 5gal, then 3.5gal which was actually an excessive amount to cause the flush action.

With the advent of water saver regulations they designed the bowl so that it would retain approx 1 to 1.5 gal as the trap seal, then they determined the minimum amount of additional water it would take to cause the flush, which works out to be 1.6gal.

If you lower the standing water in the bowl, not only does that risk the trap not sealing correctly, it also starves the bowl for water during the next flush resulting in an incomplete flush, as is described by Plumbman after he removed the trap primer line.

Take my word for it, the level of water in the bowl and the level in the tank are both critical if you expect the water closet to flush as it is intended to do.