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.

[Folkie]

So I ended up following Javi's advice and cut the bugger out, just replacing it with a piece of PEX.

I had planned on replacing it with a quality Watts brass vacuum breaker, but after I got it I realized that while it might not blow apart like the plastic one it can still leak if the float doesn't seat correctly. Since we store valuable stuff under the sink (toilet paper) I decided it wasn't worth the risk. I also determined based on how I use the tank flush that it was extremely unlikely that I would ever have a situation where there would be a chance of back siphoning the black tank.

If that assessment is incorrect my choice would be to install a check valve instead. I marked the tubing so if I later decide to install a check valve or the Watts I can orient it in the correct direction. I will still use a vacuum breaker on the hose to protect it and the water supply.

For anyone considering a similar mod, it helps to have 3 hands when operating the PEX pinch clamp tool. Not that there would be room to get a 3rd one in the cramped area. I had one fitting that slipped out of the PEX a little when I crimped it so I had to redo that side.

[Javi]

Originally Posted by Folkie

So I ended up following Javi's advice and cut the bugger out, just replacing it with a piece of PEX.

I had planned on replacing it with a quality Watts brass vacuum breaker, but after I got it I realized that while it might not blow apart like the plastic one it can still leak if the float doesn't seat correctly. Since we store valuable stuff under the sink (toilet paper) I decided it wasn't worth the risk. I also determined based on how I use the tank flush that it was extremely unlikely that I would ever have a situation where there would be a chance of back siphoning the black tank.

If that assessment is incorrect my choice would be to install a check valve instead. I marked the tubing so if I later decide to install a check valve or the Watts I can orient it in the correct direction. I will still use a vacuum breaker on the hose to protect it and the water supply.

For anyone considering a similar mod, it helps to have 3 hands when operating the PEX pinch clamp tool. Not that there would be room to get a 3rd one in the cramped area. I had one fitting that slipped out of the PEX a little when I crimped it so I had to redo that side.

Yep.... I made up the elbows first and then bent one line out to where I could get ahold of it and then did the contournist thing on the last one.

[Folkie]

Originally Posted by Javi

Yep.... I made up the elbows first and then bent one line out to where I could get ahold of it and then did the contournist thing on the last one.

Great minds think alike Tried the same. Did the hard to reach one first, but then the easier to reach one still managed to slip out due to tension from the first side.

[flybouy]

Behind the sink in the bathroom is the "easy access" install. I've read where some models have them in the wall of the shower.

[sourdough]

Originally Posted by flybouy

Behind the sink in the bathroom is the "easy access" install. I've read where some models have them in the wall of the shower.

Our friends from MI that winter beside us came in with a new Big Horn 2-3 years ago. First thing his black tank flush didn't work and he called a mobile RV tech. I walked out to see how it was going and they said the vacuum break was inside a wall and they had to cut a hole to get to it??? Didn't go see what they did but it sounded bad enough - and like a ridiculous place to put it.

[dutchmensport]

I pump the pink through the black tank flush line. Made the mistake of not doing it the first year with a camper that had the flush system. Come Spring, I learned.... plastic doesn't have a chance against ice.... and one flooded bathroom.