Bathroom Sink White PEX Piping?

[Folkie]

I have a question for our forum experts. While cleaning out the cabinet under the bathroom sink I got to wondering why there are 4 lines going up to the faucet. There are the usual blue and red lines and 2 white lines. I first thought that maybe they used the faucet to T off to the shower. I then looked in the access under the shower and saw there were Ts for both the blue and red lines under the shower that feed the shower faucet. I then saw that one white line appears to travel forward under the floor of the trailer. The other looks like it is headed over to the passenger side of the trailer.

Does anyone have an idea what these lines are for?

[flybouy]

Red and blue are hot & cold to the faucet. The other two runs to the outside connection for the black tank flush. It runs behind the sink, connects to a back flow preventer than downbto the black water holding tank.

[sourdough]

Crawl under there and look at the top where those 2 white lines connect and see if you don't see a little black doohickey sticking up there.

[CedarCreekWoody]

That is an anti-syphon valve atop those white lines.

[Snoking]

Also noted to fail and leaking water into the interior of your trailer while flushing the black tank.

[Folkie]

Thanks everyone for all the responses!

Guess I will have to stick my head in there tomorrow with a mirror and get a better look. Never would have thought about the black tank flush! The line headed forward must go to the outside connection. The other line heading to the passenger side must circle back to the black tank.

Also thanks for the heads up regarding potential leaks. I'd better run some more anti-freeze into the flush line too. I don't think I put in enough to fill all that pipe.

[chuckster57]

Originally Posted by Folkie

Also thanks for the heads up regarding potential leaks. I'd better run some more anti-freeze into the flush line too. I don't think I put in enough to fill all that pipe.

If the anti siphon valve is working, you’ll never get that line filled. Liquid drains when your not running water under pressure. I might be wrong (wouldn’t be the first time) but I don’t think you need to winterize that line.

[Folkie]

Just want to make sure I displace any water left in the line, I don't expect all the anti-freeze will remain in the line.

[Javi]

Originally Posted by Folkie

Just want to make sure I displace any water left in the line, I don't expect all the anti-freeze will remain in the line.

This is what the 27 cent piece of plastic junk will look like.. Best thing you can do with it is replace it with Pex 90` elbows and then use one these on the hose

[Folkie]

Turns out I am already using a vacuum breaker on my hose because I didn't know the other device was in the system.

[Javi]

Originally Posted by Folkie

Turns out I am already using a vacuum breaker on my hose because I didn't know the other device was in the system.

Also, be careful to not use more than 40 psi of either water or air pressure cause all the tank wash parts are plastic..

[LHaven]

Originally Posted by Javi

This is what the 27 cent piece of plastic junk will look like.. Best thing you can do with it is replace it with Pex 90` elbows and then use one these on the hose

I deleted my post. I misunderstood your suggestion. You're using the brass dingus on the hose, not installing it under the sink.

[Javi]

Originally Posted by LHaven

I deleted my post. I misunderstood your suggestion. You're using the brass dingus on the hose, not installing it under the sink.

Yep.. my dedicated flush hose has the brass vacuum breaker and a pressure regulator on it as a precaution against blowing the plastic spray bar in the tank to pieces and to prevent the small chance of siphoning from the tank.

[Folkie]

Originally Posted by Javi

Also, be careful to not use more than 40 psi of either water or air pressure cause all the tank wash parts are plastic..

Another important consideration.

[JRTJH]

I simply blow air through the black tank flush system, then remove the anti-siphon valve, shake all the water out of it and lay it on a paper towel under the vanity. In the spring, I'll reinstall it and go from there. I replaced the "cheap plastic flood maker" with a brass anti-siphon valve from the lawn irrigation section of Lowe's.

If you blow air through the system, you'll effectively remove the water/freeze damage potential, so no need for any antifreeze for the black tank flush plumbing. When you remove the anti-siphon valve, all the water remaining in the line will "flow down to the nozzle in the black tank and to the hose connection on the side of the trailer.

[Folkie]

Originally Posted by JRTJH

I simply blow air through the black tank flush system, then remove the anti-siphon valve, shake all the water out of it and lay it on a paper towel under the vanity. In the spring, I'll reinstall it and go from there. I replaced the "cheap plastic flood maker" with a brass anti-siphon valve from the lawn irrigation section of Lowe's.

If you blow air through the system, you'll effectively remove the water/freeze damage potential, so no need for any antifreeze for the black tank flush plumbing. When you remove the anti-siphon valve, all the water remaining in the line will "flow down to the nozzle in the black tank and to the hose connection on the side of the trailer.

I have to check those out

[JRTJH]

Here's one type found at Lowe's. https://www.lowes.com/pd/Cash-Acme-B...ker/1000385647 The "trick" is finding the fittings to connect it to the plumbing under your sink. Not impossible, but, at our Lowe's, the fittings are "around the corner in the next aisle".....

[Folkie]

Thanks. I saw that one but none of my local Lowes have it. Just ordered a Watts on Ebay. I was going to ask how you configured the piping. Not even sure yet if I can get it in the space.

Still have some concerns about a vacuum beaker under the sink. My limited experience is that they will all leak at some point, but I get why you want one there.

[Folkie]

John,
I just went out to look at the camper. I can just barely see the existing plastic vacuum breaker with a mirror and flashlight as it is jammed up to the faucet! Can't figure out how they got it in there unless that was put in before they mounted the sink. Guess I'm going to have to get some smaller hands before I take on this project.
Phil

[JRTJH]

On my trailer, I can pull the white PEX down about 6" or so. That gives just enough room to change things out. It's an "exercise in frustration" to be sure...

IMHO, for what it's worth, that $29 plastic anti-siphon device is the plumbing system's "weakest link"... I've known more people who flood their trailer using the black tank flush system (with that device leaking under the sink) than any other "plumbing malfunction"....

No matter what you do, even just "replacing it with a "direct section of PEX" will help assure you don't have "gallons of unexpected water under the bathroom sink".... I changed out mine in our Springdale the same weekend my DW did the "alarmed scream" letting the entire campground know that I'd just dumped about 20 gallons of water into our bathroom vanity.....

NEVER AGAIN !!!!!