My local church is looking to put in two new bathrooms in the basement so that restroom facilities are more accessible to the food pantry clients. I'm part of a committee that is trying to come up with specifications for this project.

One point of discussion is tankless versus tank toilets. In our existing upstairs bathrooms, we are currently using tank toilets.

It's my understanding that you need 1" supply lines for tankless. I believe we have at least 1" water main if not larger due to the size of the church (15K sf?) and the use of sprinklers. I read that the advantages of the tankless is that they take a bit less space, use less water, have better flushing and are more reliable to operate.

Is this correct?

Are there any cost differences (e.g, tank is cheaper than tankless?)?

We do have a septic system so it would be advantageous to use less water if possible. I'm planning to chat with our plumber but if you have any advice, it would be appreciated. Thanks!