2023 25' Globetrotter
2021 16' Bambi
Forest Lake
, Minnesota
Join Date: Mar 2021
Posts: 902
Black Tank Flush Check Valve?
Our 2021 Bambi 16' RB black tank flush stopped working. When we hook up a hose there is no water running through the system. I suspect the check valve is broken or stuck. I can't figure out what it is and where it's located. I tried looking through the parts book and for any diagrams, but there's nothing specific. If I trace the line there appears to be a vacuum valve I can feel (one of those with the round cap on it) behind a panel in the closet but it's not accessible without some major surgery to remove the panel. Is this it? Or is there an inline cylinder type valve somewhere else?
Also, when I winterized last year, I blew out the line with compressed air, could this have damaged it?
First I'd check the flush hose connection for a clogged debris screen.
The plumbing side of this has a backflow preventer, pic below. Allows water to flow into flush nozzle but does not allow water to flow back.
And possibility of nozzle being "covered up" is possible and if operated w/o debris screen nozzle might be plugged.
Access, not sure on your rig and mine its via an access panel in the pan I made during valve R&R.
Damaged by using compressed air, unlikely. The system has open holes in the nozzle and its PEX pipe. If you burst something and then attached hose and ran it, that would make for a good quick water leak.
The black round cap thing is a studor air admittance valve for the lav basin I bet.
2023 25' Globetrotter
2021 16' Bambi
Forest Lake
, Minnesota
Join Date: Mar 2021
Posts: 902
Thanks! I think what's hidden behind my panel is the device you have pictured which would be the check valve. I did take apart the hose connection and it was unobstructed. I'll see if I can get it out without marring the panel. With our tiny Bambi most everything is stuffed into a cramped location.
I believe this is a warranty item, but last time we got service it took two months for the next appointment and we'd like to have it working this summer, so looks like I need to do the work.
I bought my 2016 Sport 22fb from a couple about a year ago. The former owner told me, as he was describing the trailer amenities, that he never did use the black tank flush. So, I had no expectations for it’s use my first outing. I plugged in my hose and turned it on……crickets! Hmmmm.
I read these forums and found that there may have been a rash of installs of THAT VALVE, that were installed backwards. And, sure enough, when I took off the valve and reversed it….VOILA!!!
My valve in the 22fb is easily reachable from a panel in the closet. Sorry if yours isn’t easily accessible. It was a 20 min fix.
2023 25' Globetrotter
2021 16' Bambi
Forest Lake
, Minnesota
Join Date: Mar 2021
Posts: 902
Thanks, I should have mentioned it was working just fine last season and worked for a bit this year. Sort of strange he didn't flush his tank unless he had some other method.
. Sort of strange he didn't flush his tank unless he had some other method.
We all had to flush the tank by filling the toilet or pouring a pail if water down the toilet for many years before they started installing flush spray nozzles
The black tank flush can become clogged up with dry hardened feces. The
Airstream Factory Service techs said the nozzle is clogged, but they can blow it out with the Jackson Center city water pressure. They did that. If you have low water pressure, try using compressed air at higher and higher setting alternating with what water pressure do you have.
guskmg
2023 25' Globetrotter
2021 16' Bambi
Forest Lake
, Minnesota
Join Date: Mar 2021
Posts: 902
As an update and for anyone following along with a Bambi 16'. I was fairly convinced the check valve was the issue. The only way to access it was to deface our closet and cut a hole in it (now it will be an access panel - new feature?). The check valve has a coupling on the tank side so I detached it and hooked the hose up to the flush. If the check valve is broken then no water should come out, but low and behold it flowed through the check valve.
So, @guskmg is correct - we have a clogged sprayer. Before this surgery I did try hooking up the air compressor and chickened-out at 80 PSI afraid I might burst something. Our water pressure is pretty good, so not sure what else I can do. I'll have to research other techniques as well.
2023 25' Globetrotter
2021 16' Bambi
Forest Lake
, Minnesota
Join Date: Mar 2021
Posts: 902
An update, it's working! There's some weirdness which someone who understands the plumbing system might understand, but I'm at a loss. We took it to a dump station to empty the tank before refilling and adding some tank cleaning agent to hopefully get rid of the supposed clogged sprayer. We hooked up the flush to a water source with higher pressure than home - didn't work. We filled through the toilet and flushed the tank out a couple times - hooked up the flush again - didn't work. My wife ran water into the shower just to clean it out but the drain was clogged (wasn't clogged last time she used it). She put a knife down it to see if anything was an obstruction and lightly pushed something and there was a woosh, drain worked, and lo and behold the tank flush started working. I'm guessing it was something to do with the back flow preventor(s), but no clue.
J/K first i had to cut open a panel to access/replace mine. decided to make lemonade and installed a small hvac grill so as to circulate warm air from a small 110 heater during cold weather. used t-nuts and small bolts to make the grill easily removable. will look for thread if you're interested
note the part is vac breaker and check valve. Brass vac breaker then to the horizontal checkvalve. separate parts. the AS connection has a BF component. As part if the above i removed the BF par and use a separate BF part on the hose end at the connection. seems i was having winterizing problems pushing all the H2O up to and thru the VB/CV. making the BF exterior allowed that little bit of water to flow back to the connection when i remove the non pressurized hose. No contamination as it's all pre check valve
i use air max 55psi to winterize and also add an enzyme toilet additive (happy camper etc. ) with a capful of liquid calgon. sometimes it us best to treat with the above, fill the tank 80%, let it sit overnight, go for a stop/go slosh it drive, then dump. helps clean the sensors and the BW spray head.
a great visual of the operation of the vac breaker/ck valve. Note this is the OEM ones where it is one combo valve.
JeffKim: Yours in the post and mine is the newer brass and grey plastic CV. (my oem replaced after an OTR cold freeze....JC maybe using the brass as OEM now)
you said ..."The check valve has a coupling on the tank side so I detached it and hooked the hose up to the flush. If the check valve is broken then no water should come out, but low and behold it flowed through the check valve." this seems to be reversed?
As I understand it the flow is (in your picture) up from the right vertical and thru the Vac Breaker, left thru the check valve and down thru the ell to the tank sprayer. If you hooked up before the brass, and no water cam out, yes likely the CV. If you hooked op to the vertical connection on the left to the tank and no water came out it is likely the sprayer as you have bypassed the vac Br/ck valve
Gary the drawing was actually from Peter (otra15) but fit for me ws we have the same 20 and only 2 months built apart. in the one image the BW connection is off to the left but enters below the FW connection elevation wise. mine crosses under, turns up to the vac br exits the side to the ck valve and then turns down headed fir the sprayer. ihave thought of removing it all and just use a ss flex hose with my external BF as sometimes winterizing is a pain.
Gary here is a pretty crude drawing of my setup. As you can see there is a low spot between the BW connection and the Vac/Br ~ Check valve setup. This low spot is always a tough winterization. This discussion triggered my sr memory function... I had intended to replace this low section with a nipple/ell at the interior side of the BW connection then to a 12" SS flex hose up to the Vac/Br. This hopefully would eliminate the low spot but it's pretty tight there and I was having trouble getting the hose threaded onto the ell the day before the CA trip. Needless the refer issues on that trip put this summer functional mod on the back shelf.
As you can see our set up is a loop as opposed to the diagram's less complex in>up>over>down> over tank sprayer.
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