Move to 1” pex? – GreenBuildingAdvisor

A few years ago I replaced my trunk and branch polybutylene supply with pex, using a site built rectangular manifold, per a FH article.

At the same time I added a tank that helps my ph and UV treatment.

Now when I flush the toilet the pressure/flow drops everywhere, hot or cold.

I added a pressure gauge before the manifold, and it drops a lot more there than at the pressure tank, even if I bypass the UV and ph tank and remove the filter element.

Seeing all the fittings I have, and since they are smaller diameter than the 3/4” pipe I used, I’m thinking I need to move to 1” at least to the manifold. That make sense?

I wish I understood flow physics, and the impact of smaller fittings.