Black tank sprayer plumbing question

Well it seems that my tank sprayer has broken. While checking on the plumbing of the sprayer I saw something that looked unusual in the way it was plumbed, so I thought I would check and see if this is standard plumbing practice on the sprayer.

From the spayer water connection in the ODC there is a blue PEX tube that is connected on the back side. following the blue PEX is over to and up the wall cavity between the bathroom and Kitchen cabinets. It appears to loop back down and then runs back over to the front (of trailer) to the front side of the black tank. It then is connected to a white tube (looks like the same tube that the outside sprayer uses) and then proceeds to the tank sprayer (I haven't opened the bottom up to verify as yet). My question is why does the blue PEX need to loop up in the wall cavity and back across to the tank? There must be over 18 ft. of blue pex in this run just the what may be 4 to 5 ft.

If I have to replace the tank sprayer, can I cut this blue PEX down to eliminate all the extra?

I had read about the "rats nest" of wires and plumbing under there, but can't believe the waste of all the extra cables and plumbing can be cost effective. I may have to find time to clean it up, or better yet maybe Heartland should send someone out to straighten it up (ya right).

The blue PEX line loops up into the wall cavity to connect the anti-siphon valve in the system. There is some RVIA code that dictates putting it up there where it can fail and cause the most damage. In my rig, the PEX line is red and connects to a white flex line leading to the sprayer on the door side of the tank. I think some folks have eliminated the valve altogether and just straight-lined it to the sprayer. If that poses a problem, I don't know, but if mine fails, that's what I'll be doing. Since the connection in the UDC broke and I replaced it with a city water connection with check valve, I'm not too concerned about backflow into the water system.

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Thanks John, our areas look pretty much the same. Took me a minute to figure out the reasoning for the anti-siphon to city water, I guess it could happen if you left it connected to city water. I need to relook at my area, in your picture you can see the bottom of the back tank and the frame brace, I don't remember seeing any of that in mine, I think it covered up.

I don't know if they put some sort of cover there or not. At least mine didn't have one. Unless it got pulled by the dealer when they installed the surge protector (since relocated twice by me) and they forgot to replace it. It wasn't there when we pulled the wall during the PDI to check the water pump leak. With the way the plumbing, wiring, and heating ducts are laid out, I don't think there was one to start with. If there was, it would look like Swiss Cheese.

I think the main reason why the check valve is so high up the wall, aside from back flow issues, is because of winterizing. The water will drain from the valve back to the tank or from the valve back out the UDC by using gravity. That way the line doesn't need antifreeze. If the valve in my unit fails it can be accessed behind the portal in the shower which isn't too difficult.

Now if your sprayer isn't working, then maybe there's some blockage in the plumbing. On the previous SOB, Styrofoam chunks from the factory install was blocking the water at the sprayer. I had to get to the sprayer, remove it and clean out the Styrofoam.

Excellent reasoning Bill. I hadn't thought about the line being able to drain for winterizing. Which begs the question. If we have a check valve at the sprayer connection in the UDC, wouldn't that block the exit of water drainage from the anti siphon valve? Some things just make you go hmmmm.

Check out this Wiki article //heartlandowners.org/mediawiki/index.php?title=Black_Tank_Flusher

Ray LeTourneau said:

Excellent reasoning Bill. I hadn't thought about the line being able to drain for winterizing. Which begs the question. If we have a check valve at the sprayer connection in the UDC, wouldn't that block the exit of water drainage from the anti siphon valve? Some things just make you go hmmmm.

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Ray... yes the water would be blocked but if the plumbing was still high in the walls a solution would to be push the release "button" on the UDC check valve like one would do when winterizing the city water connection. Or possibly blowing the line could work as well.

I'm not sure there is a check vavle in the UDC connection. When ever I take the hose loose, a stream of water flows out. I can see the resoning for the check valve being high to drain the PEX, but if the valve ever breaks, that could do a lot of damage, but not anymore than if a water supply line would break. And yes I forgot to blow the sprayer line out this year, bad me. I have to replace the water heater check valve a week after we set up for the summer, I did blow the water lines out and also pulled the anode plug out, but looing at the line out of the water tank it flows uphill, so some water must have ran back to it. It was a cold winter here, so any moisture would have been a problem.

Steve... Yes you are correct there is no check valve in the UDC! I was referring to John's mod by replacing the original blk tank inlet with a city water type connection that has a check valve.

I'm wondering if you opened the furthest tap ie kitchen to release any pressure in the lines?

The anti-siphon valve must be placed above the highest sink trap. This is by code. It's required to installed at a height above the bathroom sink trap.

No worries. For a couple of bucks, I bought an air fitting (back with the TT, actually) that will allow me to blow out the lines, regardless of having the anti-siphon valve or not. And the OEM B&B Molders UDC fitting is not a check valve, just a black plastic tube with a reduced diameter molded into the middle of it. When it broke from the hose connector on the outside of the UDC, I could not find a replacement, so that's why I used the city water fitting. Same outside flange and screw hole pattern, but brass with a check valve.

I would think that if you can route the hose with a downward slope toward the sprayer then it will self drain and no longer spit back at you when you remove th supply from the city water.

DX Either I missed something or I'm confused, how would opening the kitchen faucet affect the tank sprayer?

SLJKansas said:

DX Either I missed something or I'm confused, how would opening the kitchen faucet affect the tank sprayer?

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DX might have mixed something up. The tank flush line is probably the only one that is not somehow connected to the rest of the plumbing system. Opening a faucet would not relieve pressure in that line. Doing so does relieve residual pressure on the overall plumbing system after you've shut down the city water connection or the water pump, though.

With my tank flush now set with a check valve at the UDC, I can either just press in the check valve tab to relieve pressure (and get wet), or hook my air fitting to it and blow it into the tank. Whatever is between the tank and the anti-siphon valve should drain into the tank on its own once the incoming flow is stopped.

SLJKansas said:

DX Either I missed something or I'm confused, how would opening the kitchen faucet affect the tank sprayer?

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Didn't mix anything up as I was referring to your statement that you had "to replace the water heater check valve". Just offering a thought on how THAT failed! One can't clear any residue water near it, like the city water check valve by manually opening it (pushing the release button), so, by releasing pressure in the lines at the taps, the fresh water in the Pex T would not be pushed up against the hot water check valve where it could easily freeze. It doesn't take much of a freeze to damage these check valves!

On edit: I should add that this is what I do when using antifreeze. When rereading your post, it appears that you don't. So as you said initially, I agree, residue water running back would have caused the check valve failure. Sorry for the confusion!

Thanks DX. I do leave all the faucets open after I blow out the lines, and it usually works well. But this last winter with temps down below the teens for such a long time, even with a electic heater running, It was just too dang cold.
Maybe rerouting the the waer line off the HW down a little and "T" in a shut off with a hose out the bottom,Similar to the water tank, would make it a low point drain so water would run back into the backflow. This may be a good mod and save a lot of backflow valve problems later. Boy may brain kicks in once and a while. I hope I remember to do this.

My comment about mixing things up was due to the conversation revolving around the black tank sprayer system, not the water heater. Until the water heater entered into the conversation, opening a faucet would have no effect on what was being discussed. I agree, to winterize and de-winterize, you have to open the faucets. No slam was intended.

We're good, no slam read into the post.