Can a gravity flush toilet be swapped out for a pressure-assisted toilet? Are there any differences in plumbing, mounting, etc.?

2 Answers 2


It looks like there's no difference in plumbing requirements from this installation guide.

This regular toilet installation guide lists the drain and vent requirements:

it requires its own 2" minimum vent and a drain of at least 3" in diameter

As far as retrofitting a pressure assist vessel into an old gravity flush toilet, I wouldn't try it. Pressure assist toilets are designed differently than gravity flush ones. Flushmate's website warns:

The FLUSHMATE® Pressure-Assist system cannot be retrofitted into a standard, gravity-fed toilet.

There might be a retrofit kit out there somewhere, but I'd be wary about how well it would work.


Yes it can. There are no differences on the outside.

There are even some pressure-assist valves that can be retrofitted into existing toilet tanks.

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