What Is the Air Gap/ Check Valve behind My Shower Access Panel?

A couple of days ago I was in the shower and DW flushed the toilet and I thought uh oh, the water pressure is going down. Well it did for a moment and then when the water from the toilet stopped, WOW the water pressure in the shower went up by 100%! Great pressure! I was happy, but soon found out as soon as I shut it off and turned it back on, it was back to the low pressure again.

After doing a bit of troubleshooting, I found that by turning on the sink or flushing the toilet AFTER the shower is running, I get the good pressure. Once the shower is shut off and turned back on, same old low pressure, as before.

I opened the plumbing access screw off cap in the shower and there is what looks like an air gap, or check valve type device in line with one side of the water line, or the other. Hard to tell.
I can only assume that this is the culprit causing the low flow. What seems to be happening is when the shower is running there is an obstruction or a diaphram that is restricting the water flow. When an alternate water source is turned on, ie sink, toilet,, it is enough to pull it back the other way and increase pressure in the shower.

Does anyone know if there is a filter, or any user serviceable parts in this thing before I start tearing it apart? Also what are the ramifications of removing it altogether if that is possible?

Maybe this could be in "ask the factory", but I thought it would get viewed more here.

Thanks Trace

Chances are that what you are looking at has nothing to do with your fresh water system. I'm betting it's the backflow preventer for you black tank flush system.

I believe that Branson4020 is correct. What you are looking at is the backflow preventor for the black water tank flush.
Now, if you want better pressure in the shower I recommend getting the Oxygenetics shower head. LIKE THIS.

Peace
Dave

cookie said:

I believe that Branson4020 is correct. What you are looking at is the backflow preventor for the black water tank flush.
Now, if you want better pressure in the shower I recommend getting the Oxygenetics shower head. LIKE THIS.

Peace
Dave

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Thank you both. I would have thought the black tank flush would be a home run from the black tank hook up in the UDC to the tank. Why would they have it routed through the back of the shower? Just curious.

Dave , I have the Oxygenetics. and it works okay. However, under the circumstances I described above, it works GREAT!

I need to figure out how to keep that better flow rate going without having to open the door, reach out and turn the sink on and off, everytime I turn the shower back on to rinse. Shipboard shower style, you know.

I would think there should be something I could do to overcome it.

Thanks, Trace

It may be your pressure regulator acting up. Opens to feed multiple water demands, does not close back down for just the shower.

TedS said:

It may be your pressure regulator acting up. Opens to feed multiple water demands, does not close back down for just the shower.

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Ted,
Thanks I'll check that. Im not sure whether I have an extra one with me.

TANDT said:

Thank you both. I would have thought the black tank flush would be a home run from the black tank hook up in the UDC to the tank. Why would they have it routed through the back of the shower? Just curious.

Thanks, Trace

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Trace, the backflow preventer is routed up there because of RVIA or some other code. It has to be higher than the highest fixture in the coach. Aftermarket units are available that are routed more direct.

Ray LeTourneau said:

Trace, the backflow preventer is routed up there because of RVIA or some other code. It has to be higher than the highest fixture in the coach. Aftermarket units are available that are routed more direct.

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Ray,

Thank you. That is what I suspected. It wouldn't seem to make sense that the black tank flush would not go straight to the black tank.

So you are saying, it is inline on the fresh water feed to the interior of the coach, correct?
I don't think it is functioning correctly and is hampering the water pressure to the coach somehow. I need to figure a way around it, or to replace it, without jeopardizing anything. Trace

NO, the black water flush is has its own feed to the tank, it is not connected to the fresh water inlet.

And not all black tank flush anti-siphon valves are mounted at the shower access. Some are stuffed up the wall directly behind the toilet where you can't get to them easily. If you look in the basement at the bulkhead wall, you can see where it was routed. In the basement jungle, you can see two red PEX lines in the center, with one connected to a section of white flex hose towards the bottom of the photo. That's how mine is positioned. The white line goes to the tank.

View attachment 16587

tandt, you might just remove the requlator and see what effect there is on shower flow with and without outher faucets running.

JohnDar said:

And not all black tank flush anti-siphon valves are mounted at the shower access. Some are stuffed up the wall directly behind the toilet where you can't get to them easily. If you look in the basement at the bulkhead wall, you can see where it was routed. In the basement jungle, you can see two red PEX lines in the center, with one connected to a section of white flex hose towards the bottom of the photo. That's how mine is positioned. The white line goes to the tank.

View attachment 16587

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Ted,
I read the pressure at the outside faucet and it is 80 psi. I don't know about running it straight in w/o a regulator, even though I'm tempted to.


John,
I'll take a picture of what I see and maybe that will help. In any case I would like to figure out what is causing the pressure to be low, unless I run another water source.

I'm going to have to follow your progress Trace. I too suffer from low water pressure so next time I have the coach out and hooked up I'm going to try your pressure increase trick and see if I can repeat it. I know the coach is getting good pressure just not at the shower; so if your trick doesn't work then I'll be looking for a kinked line.

Here's a link to a Wiki article with more information on this item [link].

JohnDar - Heartland began putting this item behind the shower access port a couple of years back on all brands I believe. Much nice place for it

Speedy said:

I'm going to have to follow your progress Trace. I too suffer from low water pressure so next time I have the coach out and hooked up I'm going to try your pressure increase trick and see if I can repeat it. I know the coach is getting good pressure just not at the shower; so if your trick doesn't work then I'll be looking for a kinked line.

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I had to replace the faucet in the shower about a year ago, I had to buy a cheap one because it was a Holiday weekend so I had no choice. I read somewhere that if you drill out the hole on the faucet that the hose connects to it will give you more pressure. Well, since I had to buy a cheap one I figured I had nothing to loose. I drilled out the hole close to twice the size and BINGO !! I have awesome water pressure in the shower. The cheap faucet is still going strong so you know the old saying, if its not broke, don't fix it !!
Worked for me !!

jbeletti said:

Here's a link to a Wiki article with more information on this item [link].

JohnDar - Heartland began putting this item behind the shower access port a couple of years back on all brands I believe. Much nice place for it

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So it seems from recent posts. Guess mine was before they got the hint. But since I know where it is, what it is, and what it might do, I can deal with it. The access panels I put in the basement walls allow me to inspect back there without too much difficulty. So far, so good.