Anti-Siphon valve going bad?

[wilsonxjr]

Hello RV'ers!

Trouble-shooting sewer smells in our main bath. We seem to be getting sewer odors coming from the anti-siphon valve on the black tank flush line. Is this common when the valve fails? No leaking water ... only odor. We also get a clicking sound from the valve when using the flush line.

I have been looking around the forum posts this morning and it seems to be common opinion to replace the OEM anti-siphon valve on the black tank flush line. However, opinion varies on replacing it with a brass anti-siphon valve, a simple check valve, or just remove the valve all together.

Is there a 'best' solution?

 

[danemayer]

If it doesn't leak when flushing the black tank, I'm not sure how sewer air would escape the valve.

I believe the idea of the anti-siphon valve is that if there's negative pressure on the campground water line while it's connected to the black tank flush, contaminated water could be sucked back into the water supply. The valve prevents that from happening.

It would seem like a check-valve would accomplish the same thing. But since I'm not clear on why anti-siphon valves are required instead of a check valve, I'd stick with the anti-siphon valve. And perhaps brass is the way to go for the replacement.

 

[wdk450]

I have seen add-on black tank flusher kits at RV supply stores: These add-on kits do not have an atmospheric check valve - just a simple check valve.

Here's an example: https://www.pplmotorhomes.com/parts...4yrrF9ZwdVNVvKyE0X_hh9zv6AvPAUY4aApqQEALw_wcB

 

[JohnDar]

When the cheap plastic ASV in our former BH failed and flooded into the kitchen, I pulled the lines down from the wall cavity and installed a brass Sharkbite check valve instead. Never had a problem with anything backing up to the UDC inlet port. I had previously replaced the also cheap plastic inlet (which broke) with a brass city water inlet that had a check valve in it.
If you go with a check valve and can't access it (like it's hidden in a blind wall cavity), just hang the valve as high as possible in basement and be done with it.
When a plastic ASV fails, it's probably due to the bonnet breaking off the little sticks that hold it to the body. That allows the valve seal to blow free from it and you get a fountain behind the walls. When ours failed, the top was missing and most likely never to be seen again in the bowels of the rig.

 

[Garypowell]

I think I learned about the ASV with my first RV in 1996 when it went bad and leaked. I replaced it with a check valve. 4 rigs later it’s one of the first mods I make. Never had a leak again.

Replace it with a check valve!

 

[Gary521]

Just bypass it and put in a check valve. Simple fix.

 

[wdk450]

When the cheap plastic ASV in our former BH failed and flooded into the kitchen, I pulled the lines down from the wall cavity and installed a brass Sharkbite check valve instead. Never had a problem with anything backing up to the UDC inlet port. I had previously replaced the also cheap plastic inlet (which broke) with a brass city water inlet that had a check valve in it.
If you go with a check valve and can't access it (like it's hidden in a blind wall cavity), just hang the valve as high as possible in basement and be done with it.
When a plastic ASV fails, it's probably due to the bonnet breaking off the little sticks that hold it to the body. That allows the valve seal to blow free from it and you get a fountain behind the walls. When ours failed, the top was missing and most likely never to be seen again in the bowels of the rig.

I associate my ASV failure to very high water pressure unexpectedly encountered in a desert RV park in Wells, Nevada on I-80. I found out that the municipal water supply there was from a mountain reservoir in the snow-capped mountains nearby a few thousand feet up.

I, too, replaced the ASV with a brass Sharkbite check valve when I finally got off the road for a while in West Yellowstone, Wyoming. The ASV flood splashed all over my Progressive 9260 battery charger/converter which was a much more serious problem than the loss of the intermittently used black tan flusher. I bought a cheap battery charger at Walmart in Idaho, found an RV supply store that had the Progressive charger in Eastern Idaho ($220 in 2012), and got my repairs done when I stopped for 2 weeks near Yellowstone.

 

[JohnDar]

The water source in the CG we always stayed at never went over 45 - 50 psi (my system had gages on it). The water was taken from wells on site. Between the quality of the mold design and it being stuck in a blind wall cavity where it could flop around at the end of the PEX tubing and smack the walls are what I believe caused the failure.

 

[wdk450]

BTW, if you DO want to replace the plastic ABV with a brass equivalent, Sharkbite has the brass valve with 1/2 pipe threads for $16.95 (p/n 17383-0000LF), and 1/2 inch pipe to 1/2 inch PEX fittings for $7.53 (p/n U120LFA).

 

[wilsonxjr]

Thanks all for your comments and suggestions! I will replace the ASV but that's an easy-access fix. More urgent fix was that the elbow connection from the flush line in to the black tank itself wasn't screwed in all the way and was leaking. Frustrating that it just needed a couple more turns to snug-up ...