Why does my upstairs toilet flush partially but the downstairs toilet flushes completely?I live in a traditional split level home built in 1968. The toilets are one above the other.

jorkan, will the toilet flush completely if you hold down the handle? Take the top off the tank and watch inside the tank as you flush. Is the handle lifting the flapper all the way? Is the flapper worn out? Toilet rebuild kits are inexspensive and easy to install.