Newbie FW system question

[TheHandyDan]

I'm a recently new owner of a 1960 Safari. I plan on redoing the plumbing with PEX so I decided to get the lay of the land with the current system.

I was expecting to see the system would be fed by two sources... either the main fill line or the FW tank.

In other words, I expected to see a valve after the main water line to either direct the water into the FW tank or into the main system directly.

Then the FW tank would go into a strainer, then the FW pump and into the main system from there.

Check valves would prevent the water from one source going into the other line.

So I expected to see something like this...



Instead, I found the main water line just goes directly into the FW tank. That leads me to believe the main line must fill the FW tank and pressurize the entire system if the trailer is running on the main water line. Does it just flow right through the pump or do I need to run the pump too?

Here's what I see in the trailer...



Am I diagnosing this correctly? Is this the way it's supposed to be or should I do something different when I outfit it with PEX?

[TheHandyDan]

Well, nobody replied but I thought I'd post what I wound up doing.

I realized the fill port wouldn't likely hold water pressure if I tried to use it as a city water connection in addition to fresh water tank fill. There is (was) no city water connection to the trailer so I would have to either run the system on the pump all the time or install a separate city water connection.

I was planning on replacing all of the original copper lines anyway so a complete re-do was already in the cards - why not just add a city water connection?

You can read more about it and see photos on this link to my blog.

This Old Airstream: What Goes In...

[Al and Missy]

The newer trailers have the fresh water line connected in as you showed in your first picture with one exception. The toilet for sure and maybe other appliances and the plumbing are intended for use with water pressure of about 35 psi. City water can be 75 psi or more. The new trailers have a pressure regulator at the city water inlet. Also, i believe there is a check valve in the newer pumps to prevent flow from the city water into the tank.

Al

[nrgtrakr]

Google "Airstream Plumbing Diagram" lots of hits ...

[Wayward]

The 12v pump output and the city water feed, both plumb directly into the trailer's pressure lines.

You should be able to tap the city feed in where convenient, but will need a check valve to prevent the pressurized city water from back-flowing into the pump and FW storage tank.

As mentioned above, a regulator is essential. RV park water pressures are all over the place. If you can find a place to fit it, the solid brass residential types might be a better choice than some of the plastic ones.

I've attached a typical Airstream diagram if you do not already have one.

[nrgtrakr]

The copper on our 75 was a disaster from bad repair jobs and new ruptures, so a couple of changes when I replaced with PEX ...
• City water in check valve replaced with a ball valve so it doubles as the winterization drain.
• At the pump - check valve on the tank side to keep the pump primed, ball valve on the system side to isolate the fresh water tank and pump when not in use.
• New adjustable regulator set to 30 psi.
The new plumbing is sloped good enough to not "require" antifreeze.

[TheHandyDan]

The Revolution pump I installed has a built in check valve to keep the city water from backfilling the FW tank.

The City Water connection has a built in regulator and check valve to drop the pressure (if needed) and to keep the FW pump from pumping overboard.

I also installed a single drain to drain the system except I have one spot on the hot water side that won't drain. I'll have to blow it out with air or fill it with anti freeze... although it's only PEX in that area (no fittings) so won't that withstand freezing?

The mess of copper I took out had expanded considerably in several areas. At first I thought it was 1/2" tubing with 3/8" fittings - but the tubing was smaller than 1/2".

It's a nice, clean installation now.