I need to replace my 86 gallon bladder tank. Can I replace it with a larger size, any benefits from doing so? I live in a two-story house, and there is one bathroom downstairs that has always had low pressure.
I will install it myself. Do you have a recommendation for a supplier and also a particular brand or two? I live in Northern California.

A larger tank will give you more water between the times you pump has to come on, which is suppose to be good for you pump life. A regular tank (with out a bladder) will give you effective use of 1/3 of its size when cut on/off pressure is set to 40/60 lbs. In your case that would be 30 gallons if you had a regular tank.. A bladder tank is suppose to give you more effective use for its size. Although I don't think I understand how. It does eliminate the need to periodically drain your tank because it has become water logged.

Changing the tank will not fix the lower pressure of the bath. Why are you considering changing the tank?

86 gallon is already a large size. While it would lengthen your pump cycles, it would have nothing to do with downstairs pressure. Kind of strange for the low pressure bathroom to be downstairs. Probably more of a volume issue than pressure.