To answer your question more accuratly: IT Depends.
Many RV's have a "Quick Fill" type valve, this is a valve that lets you fill the on-board tank from the city water inlet... You can choose to feed the city water straight to the storage/supply tank or directly into the RV's plumbing.
Now: One of the places I park is noted for high chlorination and in that park I fill the supply tank and let it sit a bit so the bleach bleeds off (Does not take long, like 5 minutes). Usually I feed the plumbing.
You can also fill the supply using the gravity feed as in the diagrams above if you wish.
Pressure regulator use... (Recommended) regulators come in diffeent capacities and types...
A very common regulator is about the size of a FEMALE hose connector, Has one on one end, and a male one on the other.. These can NOT pass enough water for me to take a shower
A slightly better one is the same design but usually has a bright plastic grip on the female end (Camco's has wings) Better but still no cigar as they say.
A much better one is the Sur-Flo model,, this is identical the the one built into many motor homes but read on (Try to avoid built in)
Best.. Valterra makes a unit that is adjustable, has a pressure gauge on it, I have not tested it but it gets good reviews.
When I got my Motor home 9 years ago I got a Watts, mine is 3/4" adjustable, these units have a bell shaped housing with a bolt sticking out the "Top" of the bell (The adjustmer)... It worked very well, full pressure showers.
However it has suffered from old age and the odd freezing and a lost part so I recently got a brand new ZURIN, also 3/4 inch.. I set it to 50 PSI and the needle on the in-line meter looks like it's been welded in palce while it's in use (never moves). Full shower load and it's stuck on 50,, (Moves when I unhook though).
Where to put the regulator: AT THE PARK end of the hose (Which is why I do not like built in regulators)
Filters:: Filters should go at the RV end of the hose. I recommend. Mine is home made.
