Nautilus "Check Valve" on city water connection

pthomas745

Someone noted the heavy duty warnings on the "Check Valve" in their Nautilus today, and wondered "when will I ever use it?"

I assumed (wrong!) that the check valve had the same basic function of the non Nautilus Tabs:  preventing city water from entering the fresh water tank.

But.....I looked around a bit more and found a Nautilus Repair Manual, and looked over the various threads with the great drawings of the Nautilus here on the Forums.  On Michigan Mike's pdf, he notes a "check valve" at the city water inlet, and a "check valve" near the pump. 

In the repair manual, the check valve looks like a "backflow preventer" to me.

So, how to describe what function of the "check valve" at the city water connection?  Is the "check valve" near the pump the same as the "check valve" in the non-Nautilus Tabs?

I'm barely fluent in Nautilus, but do the "city water valve positions" take over the functions of the pump 'check valves" and prevent the fresh water tank from filling when on city water?  Which makes the "check valve" at the pump redundant?

https://www.bandbmolders.com/wp-content/uploads/2018/01/Nautilus-P1-Repair.pdf

ScottG

My understanding is that the primary purpose of a check valve at the city water connection is to prevent backflow or siphoning in the event of a loss of pressure in the city water supply. This can be problematic if contaminated water from an external device (like a camper) is drawn back into a potable city water system.

Of course, the check valve will also prevent the escape of water from the camper in the event that you disconnect the supply hose, or when using the pump and FW tank.

Although I am not specifically familiar with the Nautilus, I presume the purpose of the check valve on the city water connection is the same regardless.

As for the pump, the check valve (at least in mine) is internal to the pump. It keeps the FW tank from filling when using city water, and is also important for maintaining system pressure when using the pump.   

pthomas745

Thanks, Scott.  With my house getting repiped a few weeks ago, and all the graduate study in Nautilus, I've thought a lot about plumbing recently!

Seems like: the proper term for the little flapper in the pre-Nautilus water connections should be "backflow preventer" or "check valve". 

The proper term for the pre-Nautilus device that prevents city water from filling up the fresh water tank should be "diverter valve?"

Here is the .pdf of MichiganMike's Nautilus descriptions, and you can see where he has marked the three "check valves".

https://us.v-cdn.net/5021717/uploads/editor/2t/enoq2l6qm8rq.pdf

Have the Nautilus valve settings taken over the "diverter valve" function of the water pump?

ScottG

Good questions, though again--not having firsthand nautilus experience--I can't answer them definitively.

In general, I consider a check valve (a.k.a., backflow preventer) as an in-line device that only allows flow of liquid in one direction. I interpret a diverter valve to be a valve that switches flows (manually or automatically) from one line to another.

I assume all T@Bs still have check valves at the city water connection, as well as inside the pump. However, those with the newer nautilus system also appear to have a diverter valve that allows using city water or filling the FW tank from the same connection.  

Denny16

Correct Scott G, that is my understanding of how the Nautilus is setup.  I think a check valve on the City Water connection to prevent syphoning is a RIVA requirement for RVs.  In any case it is a good idea.  What was added to the Nautilus for 2022 is a pressure regulator valve, to keep the water pressure at a preset level in thenTaB.
 Cheers