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Old 05-27-2020, 03:49 PM   #1
markcee
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San T Flush Question

The instructions included with my RV regarding the San T Flush system seem to be pretty generic in that they mention the ability of their system to flush both the black and gray tank(s). My Keystone manual doesn't provide much more definitive instruction on performing this tank flush process at all.

Question: I have a 2020 Keystone Cougar 29RLKWE. It is equipped with two gray and one black tank. I have a single San T Flush port on the side of the trailer. Does this mean I am flushing the black tank only thru this port, or is this single port plumbed to flush both black and gray?

The Swan Industries website indicates that they make systems capable of both....I just don't know if I have that option. or if there is a visual way to tell. Can I assume since I only have a single port it is black flush only?

I am coming from a Class C where my process was to dump black, dump gray and then close the gray valve, leave the black valve open and connect the hose to whatever the Winnebago nomenclature for San T Flush was, and run water thru it for a few minutes until it ran clear.

I seem to recall that my Winnebago manual was insistent on closing gray prior to running the sanitary flush on the black tank. I don't see any such warning on either the Swan documentation, or in my Keystone manual, but I'm concerned that if I have a black flush system only I may be contaminating the gray tanks by keeping the gate valves open when I flush.

Since my documentation mentions black and gray, I'm not certain if my single port flush connection is clearing out both tanks, in which case I assume I should leave all gate valves open or if I should continue with the process I used on our Class C of closing gray prior to flushing black.

I have tried to contact Swan Industries to help determine what system of theirs I have, but of course I receive their voicemail and get no call back.

Any procedural suggestions will be gratefully received!
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Old 05-27-2020, 04:43 PM   #2
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Just the black tank.
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Old 05-27-2020, 05:26 PM   #3
JRTJH
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The only "tank flush" you have is for the black tank. The two gray tanks do not have any rinse/flush capability.

The "normal process" used by most people is to dump the black tank, use the flush system if you want (not required at every dump), then close the black tank valve. Open the galley gray tank valve and allow it to empty then close that valve. Next, open the bathroom gray tank valve, when empty, close that valve and remove the sewer hose for storage.

The rationale for this sequence is this:

Always dump from dirtiest tank to cleanest tank.
The black tank is dirtiest.
The galley tank normally has food particles that "sour and stink" so it is the next dirtiest.
The bathroom tank is the "cleanest dirty water"... Dumping it last will rinse out the inside of your sewer hose, preventing you from having "black tank goo" or "soured food particles" to deal with as you disconnect, drain and store the sewer hose.
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Old 05-27-2020, 06:35 PM   #4
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When using the black tank flush I think it's best to use the flush to fill the black tank with water before dumping. I base this on thinking the more water in the tank, the better the flush. Time and circumstances permitting, I might fill and flush the black tank a couple times before finally dumping the grey tanks. Galley first, bathroom last. I also believe it's a good idea to thoroughly rinse the hose and fittings before storing them. And of course rinse down the dump area before you leave.
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Old 05-27-2020, 10:40 PM   #5
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Quote:
Originally Posted by markcee View Post
I am coming from a Class C where my process was to dump black, dump gray and then close the gray valve, leave the black valve open and connect the hose to whatever the Winnebago nomenclature for San T Flush was, and run water thru it for a few minutes until it ran clear.

I seem to recall that my Winnebago manual was insistent on closing gray prior to running the sanitary flush on the black tank. I don't see any such warning on either the Swan documentation, or in my Keystone manual, but I'm concerned that if I have a black flush system only I may be contaminating the gray tanks by keeping the gate valves open when I flush.
I never have the black valve open when any other valve is open, to avoid cross-contamination. I certainly would not do it when I was using the San-t-flush. Gray to gray is a nuisance; black to gray is a hazard.
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Old 05-28-2020, 04:25 AM   #6
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Follow Up

Thanks for the replies all. But, I believe the San T system can be used on both tanks - provided you have the model SFS200 San T installed.

I assumed it was for black tank only but the instructions from the manufacturer state "For Black/Grey" Holding Tanks, right on the top, so I wasn't sure.

So, I either have a generic set of instructions I have the dual tank model installed.
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Old 05-28-2020, 06:21 AM   #7
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Quote:
Originally Posted by markcee View Post
Thanks for the replies all. But, I believe the San T system can be used on both tanks - provided you have the model SFS200 San T installed.

I assumed it was for black tank only but the instructions from the manufacturer state "For Black/Grey" Holding Tanks, right on the top, so I wasn't sure.

So, I either have a generic set of instructions I have the dual tank model installed.
Here's the way Keystone uses the device:

The SAN T FLUSH nozzle is installed in the black tank. PEX tubing is installed from the trailer sidewall outlet (some are in the convenience center) through the trailer interior walls/floors/open spaces. The PEX turns upward, to the bathroom vanity where an anti-siphon valve, which is located high in the vanity space, usually directly under the vanity sink. The PEX is then routed down to the SAN T FLUSH nozzle and the system is connected. You can verify this by opening your vanity door, using a flashlight and count the number of PEX tubes you see. There will be 4. One for hot water to the faucet, one for cold water to the faucet and two for the Black Tank Flush system. Note that in previous years, Keystone did install some anti-siphon valves in the shower wall, but they seem to have moved away from that location in recent trailer designs.

So, "here's the deal" with the way Keystone built your trailer:

The part of your response I bolded in black: You are correct, the system CAN be used on either black or gray tanks. BUT: Keystone does not install flush systems on gray tanks. In other words, "the system can but Keystone doesn't"...

The part of your response I highlighted in red: The manufacturer of the flush system designed it to be used in either black or gray tanks. It can be installed in either. Keystone only uses it in the black tanks.

The part I highlighted in blue: Yes, the manufacturer designed it for use in either black or gray tanks. Keystone elected to use it in black tanks only.

You can confirm the above by completely emptying all your RV tanks and closing ALL tank valves. Then connect your flush system to a faucet, turn on the water, open the black tank valve in the convenience center and confirm that water is flowing out of the black tank. Close the black tank valve, open the gray tank valve in the convenience center and confirm if there is any flow from the gray tank. You won't find any flow except possibly some residual gray water not previously drained. To compliment this test, you can install a clear 3" or 6" adapter to the sewer outlet to help see what's flowing through the sewer hose outlet.

IF YOU DO THIS "TEST" BE SURE THAT YOU DON'T LEAVE THE BLACK TANK VALVE CLOSED FOR TOO LONG. YOU RUN THE RISK OF RUPTURING YOUR BLACK TANK IF YOU "FORGET AND LEAVE THE HOSE RUNNING, FILL THE TANK TO OVERFULL AND PRESSURIZE IT BEYOND CAPACITY. In other words, be careful not to explode your black tank.....
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Old 05-28-2020, 07:34 AM   #8
Tom N OH
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IF YOU DO THIS "TEST" BE SURE THAT YOU DON'T LEAVE THE BLACK TANK VALVE CLOSED FOR TOO LONG. YOU RUN THE RISK OF RUPTURING YOUR BLACK TANK IF YOU "FORGET AND LEAVE THE HOSE RUNNING, FILL THE TANK TO OVERFULL AND PRESSURIZE IT BEYOND CAPACITY. In other words, be careful not to explode your black tank.....

Every RV that Ive ever seen has a vent stack out the roof. The only way that you can over pressurize it is if your vent stack is plugged & you would have noticed your toilet gurgling back at you when flushing if that was the case. The worst that should happen is having a not-so-pleasant shower Coming off the roof.
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Old 05-28-2020, 07:35 AM   #9
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If you have 1 connection to flush 2 tanks it would definitely be a 1st for me!
How could you regulate the amount into each tank, can't trust the sensors?
Why would it be necessary to flush a grey tank, which grey tank, never have in 40+ years of rving?
If it's printed "black/gray flush" that "/" probably means "or" not "and".
If putting $$ on it, my bet is 1 connection going into the black tank only!!
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Old 05-28-2020, 03:28 PM   #10
markcee
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Thanks to everyone for their input. I'll be sure to flush black only. Appreciate all the help.
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