Water Leaks from Strange White Pipes

[adeakins]

I have a Montana legacy 3791, 2018. When I flush my black tank or use the outside shower hose, I get leaks under my bathroom sink and in my pass-through forward cargo hatch. The leaks in the bathroom, is a spray from the top of two white pipes which have been joined by some kind of black gizmo and the leak in the cargo bay is small but seems to be running down the white pipes to parallel the blue and red water pipes. I have been chasing this leak for a long time and only recently isolated to these two white pipes. I don’t know what their function is, but I have heard they are some form of back-flow preventer. In any case, does anyone have any notion as to how to stop this leak and what purpose these white pipes might serve.

[chuckster57]

That gizmo is the black tank flush anti siphon valve. They are known to fail, you have a few choices:
Replace it with a new one, figuring it will leak at some point

Replace it with a quality one from the big box hardware store

Remove it, plumb the lines together and use an anti siphon device at the hose connection.

[travelin texans]

Originally Posted by adeakins

I have a Montana legacy 3791, 2018. When I flush my black tank or use the outside shower hose, I get leaks under my bathroom sink and in my pass-through forward cargo hatch. The leaks in the bathroom, is a spray from the top of two white pipes which have been joined by some kind of black gizmo and the leak in the cargo bay is small but seems to be running down the white pipes to parallel the blue and red water pipes. I have been chasing this leak for a long time and only recently isolated to these two white pipes. I don’t know what their function is, but I have heard they are some form of back-flow preventer. In any case, does anyone have any notion as to how to stop this leak and what purpose these white pipes might serve.

Just FYI! That flush line is connected directly to your black tank, you do know what's in the black tank? Yet your connecting your outside shower hose to it?
I'd strongly suggest using a separate dedicated hose just for that purpose just to be on the safe side & never store any of the sewer connection items with or near your drinking water items.

[Javi]

Best way to fix it...

[NH_Bulldog]

Originally Posted by Javi

Best way to fix it...

100% agree with this! It fixed my issue of leaking under the sink.

One word of advice, for the sake of the health of yourself and others, use a vacuum breaker/anti-siphon fitting on the hose.

[ChuckS]

Yes the black tank uses a cheap plastic anti siphon valve located normally 8mder the bathroom sink vanity up high..

However.. the outside shower cold and hot lines do not use this valve and in no way are they connected to the black tank anti siphon valve.

Most remove the cheap plastic valve completely, some install a nice brass one, some splice the two lines together with a shark bite union.

If you are getting water leaks from that outside shower hose then you have other issues as well

If you meant that you use the outside shower hose to connect to black tank and flush it then the issue is still the anti siphon valve.

Personally.. I don’t use and never have used the s9mcalled built in black tank flush fitting

I use a Valtera King Flush adapter wit( external gate valve and flush and clean all of my holding tanks

The external gate valve prevents unwanted messes when you remove the sewer cap..

[PoCoDep]

Are you just showing a bypass?

[dutchmensport]

Originally Posted by chuckster57

....you have a few choices:
Replace it with a new one, figuring it will leak at some point

Replace it with a quality one from the big box hardware store

Remove it, plumb the lines together and use an anti siphon device at the hose connection.

There is one more option you missed: Never use the black tank flusher. Problem solved!

[Bill-2020]

Originally Posted by chuckster57

That gizmo is the black tank flush anti siphon valve. They are known to fail, you have a few choices:
Replace it with a new one, figuring it will leak at some point

Replace it with a quality one from the big box hardware store

Remove it, plumb the lines together and use an anti siphon device at the hose connection.

This is interesting to me because Keystone (as I discovered recently) plumbed the white flush line with the valve up and over top the inverter that is mounted to a 3/4 plywood mount on the ceiling, that PEX line then turns and goes back down and eventually finds its way to the tank. Now who in their right mind would put a water line directly over an electrical device??!!

And does one of these anti-siphon valves have to be a certain distance away from the hose connection? It can just go up to the ceiling of the basement and then back down to the belly, right? Any reason to extend that over another few feet then over to the tank?

[JRTJH]

Originally Posted by Bill-2020

This is interesting to me because Keystone (as I discovered recently) plumbed the white flush line with the valve up and over top the inverter that is mounted to a 3/4 plywood mount on the ceiling, that PEX line then turns and goes back down and eventually finds its way to the tank. Now who in their right mind would put a water line directly over an electrical device??!!

And does one of these anti-siphon valves have to be a certain distance away from the hose connection? It can just go up to the ceiling of the basement and then back down to the belly, right? Any reason to extend that over another few feet then over to the tank?

I believe the RVIA code calls for the anti-siphon valve to be "higher than the highest water level that can occur in the toilet bowl. That way, no matter what the "highest level of black tank water, the anti-siphon valve will be "above the flood level of the black tank system"....

Please remember, I didn't write or even consult on the codes when they were writen, so I'm just repeating what I've read, not suggesting I agree, disagree or even understand all the "FM created by RVIA".....

[Bill-2020]

Originally Posted by JRTJH

I believe the RVIA code calls for the anti-siphon valve to be "higher than the highest water level that can occur in the toilet bowl. That way, no matter what the "highest level of black tank water, the anti-siphon valve will be "above the flood level of the black tank system"....

Please remember, I didn't write or even consult on the codes when they were writen, so I'm just repeating what I've read, not suggesting I agree, disagree or even understand all the "FM created by RVIA".....

Thanks, they missed that one by two at least feet in elevation then. There is no flush line up the back side of my sink. Only over top of the inverter in the basement. Ok, there's 3/4" plywood between the two to hold back the water for a while... then ZAP!

[sourdough]

If memory serves John's assessment is correct. Now, how that fits with the actual installation in a particular RV that's anyone's guess. Had a friend that had a bad leak in his new Big Horn sitting next to us. Turned out it was the anti siphon valve but it was in a pex loop up inside his basement wall?? The mobile RV tech literally cut out the wall and made a bypass for the valve. How that worked into elevations or what purpose it served I have no idea....but they did have a HUGE bathroom up front.

[Bill-2020]

Originally Posted by sourdough

If memory serves John's assessment is correct. Now, how that fits with the actual installation in a particular RV that's anyone's guess. Had a friend that had a bad leak in his new Big Horn sitting next to us. Turned out it was the anti siphon valve but it was in a pex loop up inside his basement wall?? The mobile RV tech literally cut out the wall and made a bypass for the valve. How that worked into elevations or what purpose it served I have no idea....but they did have a HUGE bathroom up front.

My "PEX loop" is horizontal versus the usual vertical. I see a plumbing job in my near future...

[Bill-2020]

Originally Posted by sourdough

If memory serves John's assessment is correct. Now, how that fits with the actual installation in a particular RV that's anyone's guess. Had a friend that had a bad leak in his new Big Horn sitting next to us. Turned out it was the anti siphon valve but it was in a pex loop up inside his basement wall?? The mobile RV tech literally cut out the wall and made a bypass for the valve. How that worked into elevations or what purpose it served I have no idea....but they did have a HUGE bathroom up front.

Danny- your comment about “in the wall” hit me like a brick this morning when I was visualizing my plumbing over coffee in the house. The inverter I talked about hiding the plumbing is just behind (lower in elevation as well) the rear wall of the bedroom slide. The shower is then positioned there behind that location. I’m betting that this valve is up the shower wall and behind the H/C valve in the shower. That would get it up above the toilet elevation that John stated from the RVIA.

[JRTJH]

Originally Posted by Bill-2020

Danny- your comment about “in the wall” hit me like a brick this morning when I was visualizing my plumbing over coffee in the house. The inverter I talked about hiding the plumbing is just behind (lower in elevation as well) the rear wall of the bedroom slide. The shower is then positioned there behind that location. I’m betting that this valve is up the shower wall and behind the H/C valve in the shower. That would get it up above the toilet elevation that John stated from the RVIA.

Look carefully (and critically) at your trailer floorplan. Chances are that Keystone installed your anti-siphon valve, either behind the plate where the shower faucet is located (that standoff mounting plate) or, (here's the "critical" part).... Look on the cross wall that separates the shower from the room next to it. If there's a cabinet located on the other side of the shower wall, there may be a panel on the back wall of that cabinet that provides access to the anti-siphon valve.....

I have not yet seen a Keystone trailer with the anti-siphon valve "hidden in a wall so that you have to tear the trailer apart to get to the valve"... There may be some "hide and seek" to finally locate it, but usually it's just a matter of finding where it's mounted and then removing either the faucet standoff or maybe cutting a hole in the back of a cabinet on the other side of the shower wall.... Now, guessing where the valve is located in the wall and taking that "leap of faith" with a saw to make a hack job of the cabinet..... That's always an "un-nerving proposition"..... Before doing that, if you don't find a false panel in the cabinet, I'd pull the shower faucet standoff and try to judge where to cut that hole in the cabinet, but only if you can't "by hook or crook" jockey the valve to the standoff hole....

But before doing any of that, I'd first count the PEX pipes under the vanity.... If there's only 2 PEX pipes, the anti-siphon valve is not there. If there are 4 PEX pipes, follow them to the area "right up behind the faucet"... I'd guess that about 75% of Keystone trailers have the anti-siphon valve "completely hidden in plain sight" under the vanity, but unless you are a contortionist and have a very good flashlight, you will NOT find it by peeking into the vanity...

NOPE, IT'S NOT THERE is something I hear over and over, but always verify the number of PEX pipes under the vanity before doing anything else.... 9 times out of 10, the person saying "it ain't there" just missed it......

Maybe you'll get lucky and find 4 PEX pipes ??????

ADDED: Looking at your floorplan, check the linen closet next to the toilet, and that open area below the linen closet. Both of them are "prime locations" for the anti-siphon valve. There's that "big open area" under the seat in the shower that is an ideal location for the anti-siphon valve to be "hidden from any and all who might look for it".....

[Bill-2020]

John, yes, that stand off plate is what I was referencing, in there is my bet. There are no PEX lines other than hot and cold under the sink so it’s not there. As far as a false panel in the cabinets to the rear, maybe but that puts them on the opposite side of the shower. There is a false panel at the floor, next to the toilet. I’ve already been in there and left the panel open. There’s nothing in it and it makes a great space for extra TP and chemicals. I’ll be searching more in the next day or two.

[JRTJH]

Crawl into the passthrough, look aft and you'll see the 3" black ABS pipe from the toilet to the black tank. Look at the forward edge of the black tank and you should see two PEX lines going up to the shower area. Those lines are probably the black tank flush lines and may give you a hint on where they are "above the floor"... They'll be pretty close to "in line with the hose connector on the side of the trailer where you connect the black tank flush to the hose from the campground water supply"......

[Bill-2020]

I recall one white pex line to the black tank. I’ve followed it from the wet bay up to the inverter and then the pex comes back out from behind (above) the inverter and that’s the single line I recall. But I’ll look again. I’ve had to make several repairs and adjustments to the factory work as far as securing water lines, both pex and the fresh water supply side to the pump, and relocating the wall (gained another cubic foot of space. As well as relocating the route of the dump valve cables, too tight of bends made them hard to actuate. But, I’ll dive in there again and take another long look. I always find something that needs attention. I’ll get back to you soon on this treasure hunt.

[Bill-2020]

The white PEX line to the anti-siphon valve turns up and goes vertical from over top of the inverter and up behind the shower plate, then back down to the tank. I have not removed the plate in the shower to look (no sealant on hand to reseal that plate and we might be out again in a day or two).

I used a round inspection mirror and a flash light to look down and above the plywood mount that the inverter is screwed to, and that's when I verified the PEX lines do go up through the floor and into the shower wall. Taking some crude interior measurements from the shower back wall to the handles and plate, I transferred those measurements outside and they match up in the passthrough from the inside of the exterior wall to the point where they go up if you could see them.

What still gets me is why they mounted the inverter there. Given that the large 2/0 wire from the batteries to the inverter should only be so long, I know it needs to be close, but if they had just moved the inverter over to the next two aluminum floor joists and popped through the bulkhead to the batteries from there, the wire would have still reached (it would actually be closer). This would have left the PEX lines (hot/cold/tank flush) exposed so that if there were any leaks it wouldn't be over top of the inverter and it could be seen sooner. I may one day move that and get it out of harms way. First I'll replace the valve before it has a chance to break/fail and leak. It already makes a horrible noise when water is flowing through it.