Anti siphon valve

[hoserwv]

My anti siphon valve under bathroom sink is leaking. I think its when I use black tank flush. Water continues to drip, even when I quit using flush. Can I just bypass it or replace? I also saw on another thread where someone placed valve in convenience center. Where do place it and where do you purchase one?

[DQDick]

I removed mine on both of our Montana's within the first week we owned them due to all the issues they cause. I use an exterior unit on the end of a short hose that I attach whenever I flush. You can get them from most hardware stores or Amazon:https://www.amazon.com/Mueller-108-9...flow+preventer

[Montana Man]

Mine did the same. I banged on it and it started working. It just had crud on the flap. I think the best long term fix is to bypass it.

[mlh]

I replaced mine with a one way valve I bought at the hardware. You can just bypass it. It’s to make sure dirty water doesn’t backup in the water system.
Lynwood

[Md.FireFighter 3791RD]

mlh,how does/would dirty water get back in the water system? Thank,s Chuck.

[mlh]

The federal government thinks if you loose pressure some somehow could be siphoned back???? It’s our federal government but then some people can find ways to do the impossible.
Lynwood

[hoserwv]

Originally Posted by DQDick

I removed mine on both of our Montana's within the first week we owned them due to all the issues they cause. I use an exterior unit on the end of a short hose that I attach whenever I flush. You can get them from most hardware stores or Amazon:https://www.amazon.com/Mueller-108-9...flow+preventer

Thanks Bob

[BB_TX]

Originally Posted by Md.FireFighter 3791RD

mlh,how does/would dirty water get back in the water system? Thank,s Chuck.

Pulling dirty water from a black tank is highly unlikely, but theoretically possible. And if possible, someone will manage to do it. Easier to visualize when thinking of a home lawn sprinkler system, which code requires a backflow preventer valve. When the public main water supply system is shut off for maintenance, or some other reason, the water left in the pipes will begin to flow to the lowest level in the system, pulling a vacuum on the water lines. And the sprinkler system could pull dirty water back into the water system without that valve. If you open a house faucet, the vacuum will pull water from your home lines back into the supply line and you can hear it sucking air. That is why, when water pressure is restored and you open a faucet, it will blow air until the lines refill with water.

For an RV a similar thing would happen to the regular water lines. But the black tank flush is a different story as the water valve is not normally open. For it to siphon water back into the supply, the black tank flush water valve would have to be opened while the supply line was pulling that vacuum due to loss of pressure. And the black tank spray head would either have to be under water (not likely), or have black water inside the head after the tank was drained. Long shot, but possible.

[BuilderBob]

I cut it out under the the floor and just put the two lines together! I have a back flow valve that I put on the hose when I flush the black tank but you don't have to the black tank is MT when you are flushing it so no real chance of any thing through it but DW likes me to use it. Happy wife happy life.

[DQDick]

If you use a Y connection to flush while the camper still has water from the other side you can tecnically syphon out of the tank. It can also happen if the watersystem in the park has a catastrophic failure. None of this is likely, but that's why they require backflow preventers on many connections in restaurants.

[scottz]

Here is a thread discussing the issue.

http://www.montanaowners.com/forums/...ad.php?t=72875

[rohrmann]

That anti siphon valve is also an airgap valve. When I flush our tank, it works great, as it has for almost 6 years, flushing weekly. When I'm done, I remove the hose and a small amount of water drains from the flush inlet, which is the water from where the valve is, as the airgap valve opens to allow air to enter which allows the water to drain out. The water in the line from the airgap valve to the flush head in the tank will also drain to the tank. This is how the system is designed, and so far, it continues to function fine. If you leave a check valve connected at the hose inlet, you must make sure when it comes time to winterize to install antifreeze to that line also, especially if you have removed the back flow/airgap valve.

[BB_TX]

Originally Posted by rohrmann

...........
. If you leave a check valve connected at the hose inlet, you must make sure when it comes time to winterize to install antifreeze to that line also, especially if you have removed the back flow/airgap valve.

Or winterize even if you do remove the external check valve. Here is pic of mine after winterizing (you can see the pink stuff in the flush lines and the shower lines). The flush line did not drain either direction with the vacuum breaker valve removed.

[Ed and Carole]

Toss the plastic valve and replace with a metal valve. This valve is there for a reason, plus tank odors will vent back through the flush line when the hose is disconnected. Also when flushing use a pressure regulator or do not over pressure the system. The flush line and fittings are the same type as used for the water lines in the rig.

[whutfles]

My bypass valve started to leak the first year we owned it. I had a wye at the campground pedestal with one hose running to the flush. I just turned off the wye when not flushing. Didn't do that more than a couple of times and noticed the valve leaking. Dealer helped me figure out that when the pressure is cut to the flush line, the water left in the hose will quickly loose pressure and then the flap in the check valve opens and lets the water drain into the lavitory cabinet. So when I turned off the flush line, they had me disconnect the hose from the camper flush connection and let the water drain back out that was trapped in the hose that hadn't reached the valve. The leak quit. I do that every time I finish flushing. I didn't replace the valve and it has worked perfect for the past 8 years with no leaks since..

[Dave W]

Another JIT thread
We have had some sewage odor this year and I've been blaming the @#$% HEPvO traps. I'll either remove that $30(!!) anti sopphon valve completely or add a Cash-Acme. Yes, those @!#$% HEPvO traps ---- not an easy fix on our HC as one is hooked at the bottom of the shower drain and the other in the sink cabinet and it's really tight there.

[Dave W]

I found a 1/2" male one end, 1/2" female plastic (PVC) swing or street ell in the irrigation section at Lowe's. Added a 1/2" close pile nipple and had a replacement for the OEM supplied trap that allowed stench in the bathroom. Total cost was $.65 for the ell and about .75 for the nipple (tho mine came from my odds and end box). It is very close to the same length as what I removed so no PEX lines mods needed so screwed right on in a couple minutes

[mtlakejim]

Originally Posted by rohrmann

That anti siphon valve is also an airgap valve. When I flush our tank, it works great, as it has for almost 6 years, flushing weekly. When I'm done, I remove the hose and a small amount of water drains from the flush inlet, which is the water from where the valve is, as the airgap valve opens to allow air to enter which allows the water to drain out. The water in the line from the airgap valve to the flush head in the tank will also drain to the tank. This is how the system is designed, and so far, it continues to function fine. If you leave a check valve connected at the hose inlet, you must make sure when it comes time to winterize to install antifreeze to that line also, especially if you have removed the back flow/airgap valve.

Would rather winterize the line than have to worry about cheap plastic parts leaking on cheap cabinets.

[DQDick]

Or, if you blow your lines with an air compresser you have to remember to blow the flush line also.

[Dave W]

I have never blown out that flusher line on the last 3 RVs we have owned - and since it only gets to around -15 here, must just be lucky