Journey with Confidence RV GPS App RV Trip Planner RV LIFE Campground Reviews RV Maintenance Take a Speed Test Free 7 Day Trial ×
 

Go Back   Montana Owners Club - Keystone Montana 5th Wheel Forum > MOC Technical Forums > It's a Dirty Job but Someone has to do it!
Click Here to Login

Reply
 
Thread Tools Search this Thread Display Modes
 
Old 06-22-2024, 01:01 PM   #1
MuscadineMontana
Established Member
 
MuscadineMontana's Avatar
 
Join Date: Oct 2021
Location: Muscadine
Posts: 19
M.O.C. #29898
Tank Flush - HOW?? 3761FL

Ok folks. Weíve had this rig for 3 years and Iíve tried to flush the tanks twice following the instructions in the wet bay to a T.. both times I ended up flooding the secondary bathroom pipes under the sink. What am I doing wrong!?! Is the flush tank faulty? All valves are open when Iím have it running, per the directions. I canít find a good video or any directions any where. Any help would be fantastic, because I donít have to have to run the old spinning water hose down the pipes.. see pictures
Attached Thumbnails
Click image for larger version

Name:	IMG_0719.jpg
Views:	26
Size:	214.4 KB
ID:	17377   Click image for larger version

Name:	IMG_0720.jpg
Views:	17
Size:	174.3 KB
ID:	17378   Click image for larger version

Name:	IMG_0721.jpg
Views:	17
Size:	233.2 KB
ID:	17379   Click image for larger version

Name:	IMG_0722.jpg
Views:	29
Size:	158.3 KB
ID:	17380  
 
MuscadineMontana is offline   Reply With Quote
Old 06-22-2024, 01:11 PM   #2
Gonefishing
Montana Fan
 
Join Date: Sep 2023
Location: Jacksonville
Posts: 218
M.O.C. #33285
I have the same unit mine is a 2021 3761fl. I have two black tanks therefore i have two blank tank flush valves. I connect a water hose to the tank flush open the valve and turn water on to the hose. I let it run about 30 minutes. Then I switch to the other tank flush and do the same thing.
__________________
Bob, Kay and our 3 pups Lily, Willis and Gizmo
Jacksonville, Nc
Retired LEO of 35 years enjoying life camping n fishing
2021 Montana 3761fl pulled with a 2022 F350 King Ranch
Gonefishing is offline   Reply With Quote
Old 06-22-2024, 01:20 PM   #3
MuscadineMontana
Established Member
 
MuscadineMontana's Avatar
 
Join Date: Oct 2021
Location: Muscadine
Posts: 19
M.O.C. #29898
So you have one valve closed and one open?. Then switch them around after 30 min? Are the grey tank valves closed or open, does it even matter?
MuscadineMontana is offline   Reply With Quote
Old 06-22-2024, 01:35 PM   #4
Carl n Susan
Site Team
 
Carl n Susan's Avatar
 
Join Date: Oct 2005
Location: Carmichael - CA
Posts: 7,540
M.O.C. #4831
The last pic of under the sink is different. Usually there are tow white Pex lines coming into an anti-siphon valve in addition to the Red and Blue lines connected to the sink fixture.

The water on the floor and on the TP. Is that from the sink line fittings or is it leaking in from behind the wall? Can you see the water dripping when the black tank flush is running?

The anti-siphon valve has been installed in the sink cabinet for a while. But it used to be hidden behind the shower wall. Maybe Montana has decided to place it somewhere new?

You only need the black tank valve (and not the shower or sink ones) open when running the black tank flush.
__________________
Carl (n Susan)
There is more to life than fuel mileage.
2012 Montana 3700RL Big Sky Package towed by a 2015 Ford F350 6.7L PSD 4WD CC LWB

Carl n Susan is offline   Reply With Quote
Old 06-22-2024, 01:36 PM   #5
Gonefishing
Montana Fan
 
Join Date: Sep 2023
Location: Jacksonville
Posts: 218
M.O.C. #33285
Quote:
Originally Posted by MuscadineMontana View Post
So you have one valve closed and one open?. Then switch them around after 30 min? Are the grey tank valves closed or open, does it even matter?
I keep the gray tanks closed. Yes I do one black tank at a time.

Just to clarify you have two flush valves one for each black tank. They are side by side. You will need to connect your hose to each one separately and open the dump valve to see which one is for what tank. On mine when connected to the left one I open the left valve for the black tank. When connected to the right one I open the right valve for the black tank just remember when connected to the flush valve to,open you dump valve. I follow these steps 1. Open dump valve 2. Connect hose to flush valve 3. Turn on water. When done 1. Shut water off 2 disconnect hose from flush valve 3. Shut dump valve
__________________
Bob, Kay and our 3 pups Lily, Willis and Gizmo
Jacksonville, Nc
Retired LEO of 35 years enjoying life camping n fishing
2021 Montana 3761fl pulled with a 2022 F350 King Ranch
Gonefishing is offline   Reply With Quote
Old 06-22-2024, 01:39 PM   #6
Carl n Susan
Site Team
 
Carl n Susan's Avatar
 
Join Date: Oct 2005
Location: Carmichael - CA
Posts: 7,540
M.O.C. #4831
The more i look at that last pic, the more it looks like the water is coming in from under the left wall. You need to find where the clear Pex lines are running. You probably have to go in through the pass through compartment and remove the back wall to see them.
__________________
Carl (n Susan)
There is more to life than fuel mileage.
2012 Montana 3700RL Big Sky Package towed by a 2015 Ford F350 6.7L PSD 4WD CC LWB

Carl n Susan is offline   Reply With Quote
Old 06-22-2024, 02:37 PM   #7
Mikendebbie
Montana Master
 
Mikendebbie's Avatar
 
Join Date: Jan 2018
Location: Austin
Posts: 2,519
M.O.C. #21044
This pic is NOT a 3761 frame - but this will give you a visual for how the tanks are mounted in the frame. Your unit has a mid-half bath and full bath in the rear. The white tank is the fresh water tank. The spec sheet for your unit says you have 88 gals black and 88 gals gray - which means you have two 44 gal tanks for each system. You may have a black and gray tank located to the rear of the fresh water tank in this pic. I have no idea if your single black tank flush connection is split to rinse both tanks or if it only rinses the front black tank - likely mounted under the basement like this photo shows. However, I have no idea where your tanks are located. I just like this photo!!!
Attached Thumbnails
Click image for larger version

Name:	IMG_1441.jpg
Views:	26
Size:	142.2 KB
ID:	17381  
__________________
MikenDebbie Aggie Ď77 in the sticks near Austin TX
2019 Chevy 3500 High Country DRW
2018 Montana 3921FB
Aussie Gus + Texas Heeler Jimmy
Mikendebbie is offline   Reply With Quote
Old 06-22-2024, 02:47 PM   #8
MuscadineMontana
Established Member
 
MuscadineMontana's Avatar
 
Join Date: Oct 2021
Location: Muscadine
Posts: 19
M.O.C. #29898
I do have 2 black tanks, but I only have 1 flush tank port. There is one to the left of it that says flush and the one to right says FILL.
MuscadineMontana is offline   Reply With Quote
Old 06-22-2024, 03:23 PM   #9
Carl n Susan
Site Team
 
Carl n Susan's Avatar
 
Join Date: Oct 2005
Location: Carmichael - CA
Posts: 7,540
M.O.C. #4831
Quote:
Originally Posted by MuscadineMontana View Post
I do have 2 black tanks, but I only have 1 flush tank port. There is one to the left of it that says flush and the one to right says FILL.
There are two black tank flush connections. The one on the left that you found. The connection to the right of it is the other black tank connection. The "Fill" label applies to the TANK FILL POWER FRESH) lever above there where you select where the shore input water will to go. That is to either the house water (NORMAL FLOW) fittings *OR* to "FILL" the Fresh Water Tank.
__________________
Carl (n Susan)
There is more to life than fuel mileage.
2012 Montana 3700RL Big Sky Package towed by a 2015 Ford F350 6.7L PSD 4WD CC LWB

Carl n Susan is offline   Reply With Quote
Old 06-22-2024, 03:33 PM   #10
BB_TX
Montana Master
 
Join Date: Oct 2006
Location: McKinney
Posts: 7,294
M.O.C. #6433
Classic symptom of failed antisiphon valve. I agree with Carl. From the pics it looks like water coming from under that wall.

Your vanity water lines are going into the left side wall. That is also the back wall of the washer/dryer cabinet. I would bet they brought all the water lines up inside that wall. Including them installing them antisiphon valve and pipes inside that wall.

It’s possible (maybe not likely) they put an access panel in the back wall of the W/D cabinet. If not (or if you can’t get behind the W/D), you will probably have to drop the belly cover under that area. Likely you will find a red pipe and a blue pipe going up thru the floor for hot and cold water for the W/D and the vanity. And also likely you will find two white pipes going up thru the floor to an antisiphon valve installed up in that same wall.

If the above is the case, the best thing to do would be cut the two white pipes, connect them together, and install an external antisiphon valve.

All speculation on my part of course. Different floorplan, but my valve was in the wall between my shower and my entry coat closet.
Attached Thumbnails
Click image for larger version

Name:	IMG_1404.jpeg
Views:	12
Size:	222.7 KB
ID:	17382  
__________________
Bill & Patricia
Riley, our Golden
2007 3075RL (recently sold, currently without)
BB_TX is offline   Reply With Quote
Old 06-22-2024, 05:04 PM   #11
Daryles
Montana Master
 
Daryles's Avatar
 
Join Date: May 2019
Location: Alton
Posts: 2,845
M.O.C. #24086
You need to find the Amti Siphon vacuum breaker valve. Trace the white PEX pipes. That's the color they use for the black tank flush.
Once you find it, replace it with a quality brass one.
Attached Thumbnails
Click image for larger version

Name:	Anti siphon vacuum breaker valve 1.jpg
Views:	15
Size:	281.3 KB
ID:	17383  
Daryles is offline   Reply With Quote
Old 06-23-2024, 09:38 AM   #12
Gonefishing
Montana Fan
 
Join Date: Sep 2023
Location: Jacksonville
Posts: 218
M.O.C. #33285
Quote:
Originally Posted by Carl n Susan View Post
There are two black tank flush connections. The one on the left that you found. The connection to the right of it is the other black tank connection. The "Fill" label applies to the TANK FILL POWER FRESH) lever above there where you select where the shore input water will to go. That is to either the house water (NORMAL FLOW) fittings *OR* to "FILL" the Fresh Water Tank.
This is correct I have the same unit.
__________________
Bob, Kay and our 3 pups Lily, Willis and Gizmo
Jacksonville, Nc
Retired LEO of 35 years enjoying life camping n fishing
2021 Montana 3761fl pulled with a 2022 F350 King Ranch
Gonefishing is offline   Reply With Quote
Old 06-23-2024, 02:28 PM   #13
Rexl1200
Established Member
 
Join Date: Jan 2023
Location: Tega Cay
Posts: 17
M.O.C. #32169
I had to replace the anti-siphon valve on our 2021, it is located right behind the 1/2 bath wall accessible through the panel in the under storage.
Same exact issue. Get a good brass replacement.
Rexl1200 is offline   Reply With Quote
Old 06-23-2024, 08:22 PM   #14
rohrmann
Montana Master
 
rohrmann's Avatar
 
Join Date: Oct 2012
Location: Box Elder
Posts: 4,768
M.O.C. #12947
Quote:
Originally Posted by Daryles View Post
You need to find the Amti Siphon vacuum breaker valve. Trace the white PEX pipes. That's the color they use for the black tank flush.
Once you find it, replace it with a quality brass one.

Not always white. They must have had an abundance of red PEX when they built our rig, and used the red to plumb the tank flush. May be hard to see, but our valve is between the shower wall and the back of the pantry cabinet.
Attached Images
 
__________________
Bob & Becky
2012 3402RL
2012 Chevy 2500HD D/A CC 4WD
rohrmann is offline   Reply With Quote
Old 06-23-2024, 09:21 PM   #15
ScaryPapa
Established Member
 
Join Date: Jan 2022
Location: COEUR D ALENE
Posts: 22
M.O.C. #30351
Just had to replace the anti-siphon valve on our 2022. It was doing the same thing, leaking under the bathroom sink
__________________
2022 Montana 3121rl Legacy
2017 Ford Platinum F350 6.7L
ScaryPapa is offline   Reply With Quote
Reply

Tags
flush, tank

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

» Featured Campgrounds

Reviews provided by

Powered by vBadvanced CMPS v3.2.3
Disclaimer:

This website is not affiliated with or endorsed by Montana RV, Keystone RV Company or any of its affiliates. This is an independent, unofficial site.


All times are GMT -6. The time now is 04:57 AM.


Powered by vBulletin® Version 3.8.9
Copyright ©2000 - 2024, vBulletin Solutions, Inc.