Backflow preventer for tank rinse

[youroo]

Originally Posted by jimh

what was it on?
on mine the one on the black water flush looks more like a vacuum breaker. i didn't really examine it though.

when we required back flow preventor at my former place of employment, it consisted of 2 check valves in series with a pressure release between.

Dont know if this is what you are asking but it was on a (V-Lite) or it was on the (black water rinse). I called it a (valve),they may call it a (vacuum breaker) or( check valve) at the time I didnt care,it was failing and flooding my trailer. Two ckeck valves and a pressure relief valve would be overkill,and also need another hole to be drilled in the floor for water discharge. Youroo!!

[jimh]

i can imagine when ur chasing a leak ur not worried abt the technicalities.
i was wondering if it was on the water inside the trailer. what i have is external between the shell and the tank. no chance of getting on the inside of the trailer.

i haven't taken a close enough look at what i have; it appears that it drains the line when the pressure is off of it.

[fivecodys]

Originally Posted by bsmall

I just had a little water trying to weep thru the threads and make a drip about every minute, so i just kept tightening it so far so good.

I'm going to order the part today.
I will report back.
Thanks for the help.

Bill

[jimh]

i looked at mine and have the same thing. just outside next and above the tank. u wouldn't want a vent inside on the black. they do put vacuum breakers on the inside that go to the gray (good argument for not contaminating gray tanks w/blk water).

what i was getting at is that a check valve is not a back flow preventer. it has to be used in conjunction with something else or another check valve to be a back flow preventer.

in ur photos, backflow prevention is accomplished by the loop and the check. if u cut out the loop, u wouldn't have backflow prevention.

sellers will call the check a back flow preventer because most think of them that way.

[fivecodys]

Originally Posted by jimh

i looked at mine and have the same thing. just outside next and above the tank. u wouldn't want a vent inside on the black. they do put vacuum breakers on the inside that go to the gray (good argument for not contaminating gray tanks w/blk water).

what i was getting at is that a check valve is not a back flow preventer. it has to be used in conjunction with something else or another check valve to be a back flow preventer.

in ur photos, backflow prevention is accomplished by the loop and the check. if u cut out the loop, u wouldn't have backflow prevention.

sellers will call the check a back flow preventer because most think of them that way.

Well..I'm confused now.
Is the photo a one way valve? Or, does it serve as a vent also?
It does have a odd shape. I can't imagine venting black tank gas into the trailer.
Now my head hurts!

[jimh]

the one by youroo looks like a spring loaded check.
the one by bsmall looks more like 2 checks. if he has changed the brass one, he would be able to tell more abt what he found.

with the loop the check should be enough insurance. only other thing, u need to see if the check is dependent on position. some will only work if mounted vertically. depends on how it is made inside.

as far as i can tell, mine isn't vented. it was very difficult to see in there. if i had to replace it, i would examine it more closely. i would tend to replace in kind (except for the plastic). there is too much abt plumbing and the why's and how's i don't know. was surprised to find vacuum breakers hidden inside the cabinet.

until abt 15 yrs ago, i didn't know that a check and a backflow preventer weren't one in the same. the term showed up on a line test sheet and i asked why they didn't just say check. was told there was more to the backflow preventer.

[fivecodys]

Originally Posted by jimh

the one by youroo looks like a spring loaded check.
the one by bsmall looks more like 2 checks. if he has changed the brass one, he would be able to tell more abt what he found.

with the loop the check should be enough insurance. only other thing, u need to see if the check is dependent on position. some will only work if mounted vertically. depends on how it is made inside.

as far as i can tell, mine isn't vented. it was very difficult to see in there. if i had to replace it, i would examine it more closely. i would tend to replace in kind (except for the plastic). there is too much abt plumbing and the why's and how's i don't know. was surprised to find vacuum breakers hidden inside the cabinet.

until abt 15 yrs ago, i didn't know that a check and a backflow preventer weren't one in the same. the term showed up on a line test sheet and i asked why they didn't just say check. was told there was more to the backflow preventer.

Ok, I think I understand. I would like to replace with the same type of part but when I call the dealer (60 miles away) I get put on hold forever and a day.
The dealer has replaced this twice already so there is no use putting another one in there.
If anyone knows of a place to check for parts, I am open to suggestions.

Thanks for the help.

Bill

[jimh]

pull it and see what u have. depending on where u live. they shouldn't be that hard to come by. home depot, lowes. if u have a plumbing supply they will have it. a spring loaded check can be mounted any way.

[jimh]

the one listed by fivecodys in post #6 looks good. my only question is is it spring loaded.
there is also one by camco that is spring loaded at Amazon.com: Camco 23303 RV 1/2" Back-Flow Preventer: Automotive
in that service, i wouldn't look at a check valve or back flow preventer as being critical. u r probably going to put one on the end of ur hose as well.
if u have a trailer or rv supply place anywhere near u, they probably have it.