Adding a second fresh water tank

[Jayco Journey]

I'm shopping for the HT Jayco 5th wheel and hesitate because the water supply tank is very limited - mostly around 42 gallons, give or take. I've always owned the Jay Flight campers because of the large fresh water capacity of >80 gallons. I would want to add a fresh water tank in the 5th wheel if I go that route. We most frequently camp at state parks so ample water supply is important. Does anyone have any ideas on the likelihood of my plan working, where you would install and extra tank in the coach, etc.

All ideas and thoughts are welcome. Thanks!

[starcraft69]

I use a soft 45 gal portable water bladder to refill tanks. lays in bed of truck and use 12v pump to transfer