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Old 09-13-2022, 12:53 AM   #1
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Brand: Thor Motor Coach
State: Georgia
Posts: 8
THOR #27776
Black tank flush clean out

Neither of my black tank fresh water flush ports seem to be letting fresh water in the tank to clean it out. They just build up pressure and nothing goes in the tank. Then when you unscrew it spews all the fresh water back out. This is on a 2022 BT36 and is the same for front and back bathrooms.

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Old 09-13-2022, 01:40 AM   #2
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Brand: Thor Motor Coach
Model: 2020 Magnitude SV34
State: Florida
Posts: 3,717
THOR #12751
It is possible that they installed the vacuum breaker backwards or they did not cut the hole in the tanks for the water to flow in from the San-T-Flush port.

Neither would be surprising when it comes to Thor.

I would get out your schematics out and start tracing the plumbing….. or if its brand new, call your dealer.
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Old 09-17-2022, 08:37 PM   #3
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Brand: Thor Motor Coach
Model: 2022 Four Winds 31W
State: Texas
Posts: 9
THOR #27889
Black Tank flush not working - our findings

Our new Four Winds 31W came from the factory with this issue. Turned out the anti-siphon/back flow check valve was reversed plumbed - apparently a common issue. Warranty fix at dealer is your best bet unless you have the correct PEX tools and skills. In our 31W, the valve is located inside the wall between the bedroom and bathroom. It's up high in the wall, I'm guessing to mitigate any chance of blackwater infiltration and mitigate any potential siphon effect. Ours was accessible thru the far left cabinet over the bed, left side panel against the wall. If necessary, you can get to the PEX piping leading up to it thru the access panel within left nightstand or to a lesser degree, the access panel under the bathroom sink. I know this because I first tried cutting the lines below and inserting 1/2" PEX couplings to reverse the flow.





After reversing the lines, I tried another flush and water started pouring out of the coach onto the driveway. I discovered the water was coming from inside the wall flooding the bathroom floor! After opening up the side wall of the upper left bedroom cabinet to expose the valve assembly, I discovered someone at the factory had nicked the PEX at the valve with a hole saw



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Old 11-24-2022, 01:07 PM   #4
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Brand: Thor Motor Coach
Model: 31W
State: Virginia
Posts: 3
THOR #27650
Posting some pictures would be helpful.
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Old 11-24-2022, 06:19 PM   #5
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Model: 2017 Miramar 34.4
State: Florida
Posts: 307
THOR #9721
This one-way valve is in the wall somewhere. Log into your owners portal for the schmatics document for your rig. It will detail exactly where it is located.
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Old 11-25-2022, 03:57 PM   #6
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Brand: Thor Motor Coach
Model: 2022 Four Winds 31W
State: Texas
Posts: 9
THOR #27889
Reversed black tank flush check valve

I unsuccessfully tried to post pics before. Will try again here.

Here's the PEX supply and return lines at the bottom of wall, under the nightstand and bathroom sink:
https://drive.google.com/file/d/1-z9...ew?usp=sharing

After I cut and spliced them to try and correct the reversed flow:
https://drive.google.com/file/d/1FY2...ew?usp=sharing

Discovering the massive leak above inside the wall, I began to open up the wall above. Here's the check valve hidden inside the bathroom/bedroom wall, access thru left overhead cabinets over bed:
https://drive.google.com/file/d/1mRJ...ew?usp=sharing

https://drive.google.com/file/d/1mSM...ew?usp=sharing

https://drive.google.com/file/d/1VH3...ew?usp=sharing

And here's the finished job with a new 1/2" brass check valve and fresh PEX tubing:
https://drive.google.com/file/d/1PSC...ew?usp=sharing

Works like a champ now.
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Old 11-25-2022, 04:04 PM   #7
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Brand: Thor Motor Coach
Model: ACE 27.1
State: Florida
Posts: 10,657
THOR #7035
Quote:
Originally Posted by BaBa View Post
I unsuccessfully tried to post pics before. Will try again here.

Here's the PEX supply and return lines at the bottom of wall, under the nightstand and bathroom sink:
https://drive.google.com/file/d/1-z9...ew?usp=sharing

Here's the check valve hidden inside the bathroom/bedroom wall, access thru left overhead cabinets over bed:
https://drive.google.com/file/d/1mRJ...ew?usp=sharing
https://drive.google.com/file/d/1mSM...ew?usp=sharing
https://drive.google.com/file/d/1VH3...ew?usp=sharing

And here's the finished job with a new 1/2" brass check valve and fresh PEX tubing:

What you are trying to post as "images" are actually shared pages. You can post those links directly. They won't work in the image box or with IMG tags.

I fixed the links for you.
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