I am putting in 5 showers and I would like to know if a 3/4 line is good

Most showers are plumbed with 1/2" so , on the surface your 3/4 should be fine. However, what are the chances all 5 would be used at the same time? Additional questions would be regarding your hot water supply, an tank cant support 5 running at the same time. Some tankless instant on heaters could do it be only very large units.

You are telling us only one piece of the puzzle. We also need to know what is the incoming pressure and developed length of that 3/4" pipe at the most distant shower. Moreover, we need to know whether you are installing these 5 showers in residential house or is it commercial property ( school, gym, spa, etc ). Furthermore, is that 3/4" a main run with 1/2" branches to each shower valve ? Lastly, are those 5 shower the only plumbing fixtures connected to that 3/4" pipe ? Please, clarify.

In my area of operation, 3/4" pipe would never fly, especially in commercial application

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Milo