In looking at the pictures of people's water tank installations, a question came to mind. Is it always required to install the pump or pumps at the lowest point? In other words, will they pick up the water if the connection is at the lowest point but the pump sits above the static level of the tank (similar to a lift tube)?
A good pump will provide enough suction to pull from the tank despite a few feet of elevation, while an 'okay' or 'poor' pump will struggle to prime in this situation. Over time a 'good' pump becomes an 'okay' pump, so it depends on how much you feel like dealing with this potential problem down the road.
My pump sits above the water heater, which puts it about 18" above the outlet on the fresh water tank. It is just a simple Shurflo pump, but it can pull a prime on its own easily. The only thing that's necessary is to have a water outlet open upstream, as the pump is not able to pull a prime while pushing against the closed pipes. But I think that's the case in pretty much all pumps unless they're immediately adjacent to the tank outlet.
We've had 4 RVs and this bus. All had (have) surflo pumps. Our only problem was in a 24 foot Winny and the pump was about a foot off the floor. When the tank got low on water the pump would rumble but not give much pressure. I moved the pump to the floor and problem solved. I guess if you think about the water tank being like a city water silo, let the weight of water help the pump. If you have the space I'd put it there.
Unions immediately both sides of the pump for rapid replacement, and ease of letting the water out for freeze protection.
I mount mine down low, superstition re: above noted, weight of water column helps the pump, hoping that it lasts longer?
Happy coaching!
Buswarrior
I agree with unions if needed. Our Shurflo has quick release plastic swivel wing nuts that detach the water lines quickly and carry an identical new replacement pump if needed. We were thinking on installing the new pump parallel with the existing one with valves but figured it as an overkill. I may eat those words if an emergency chage over is during real inclement weather. :-\
I've got my tanks on the way. The single waste tank will be 125 gallons and will mostly block the end of the rear bay on the driver's side of the bus, and the freshwater tank will sit perpendicular to that so that I can get to both the rear junction box and the fan system opposite the rear junction box. It's a little precarious at this point, so I will need to be clever about how I mount the pump and other hardware. Once the tanks arrive, I can plan more details and determine if my ideas will work. Thanks everyone!
Best put the pump on the floor Glen. Fewer problems that way. Try to use flexible hoses so you can slide it out to service it if you can.Back in a corner is OK, back in a corner behind a tank that has to be moved to get to it is not.
Jim
I mounted the pump just above the tank so that if it has a catastrophe failure it doesn't drain the tank.