i always put in both. make it like a regular rv with either use by direct hook up to water faucet, or tank with pump. also put inlet on correct side of bus.
and if you are like me, you install two pumps (one for backup) and two types of water heaters...
is bit extra plumbing, but over the years i have found the bit of extra work is worth the redundancy
Jesus Christ... Conversion in progress.