RV Trip Planning Discussions

Go Back   iRV2 Forums > THE OWNER'S CORNER FORUMS > Tiffin Owner's Forum
Click Here to Login
Join iRV2 Today

Mission Statement: Supporting thoughtful exchange of knowledge, values and experience among RV enthusiasts.
  This discussion is proudly sponsored by:
Please support our sponsors and let them know you heard about their products on iRV2
Thread Tools Search this Thread Display Modes
Old 03-22-2017, 02:34 PM   #1
Join Date: Feb 2013
Posts: 30
2008 Allegro 34TGA plugged black tank flush

Worked perfectly until 3 days ago. Now there is zero flow thru the connection into the black tank. Can't think of anything I did to cause the blockage. Tank and drain work perfectly, issue is only with the black tank flush system.

The complete lack of flow (as confirmed by a flow meter) makes me suspect it's not just some junk clogging the line, but something of a mechanical nature.

Any ideas what might be the cause of the blockage, and how to fix it? How to gain access to the tank end of the flush system?

jacksonmacd is offline   Reply With Quote
Join the #1 RV Forum Today - It's Totally Free!

iRV2.com RV Community - Are you about to start a new improvement on your RV or need some help with some maintenance? Do you need advice on what products to buy? Or maybe you can give others some advice? No matter where you fit in you'll find that iRV2 is a great community to join. Best of all it's totally FREE!

You are currently viewing our boards as a guest so you have limited access to our community. Please take the time to register and you will gain a lot of great new features including; the ability to participate in discussions, network with other RV owners, see fewer ads, upload photographs, create an RV blog, send private messages and so much, much more!

Old 03-22-2017, 06:35 PM   #2
Senior Member
Tony Lee's Avatar
Join Date: Sep 2012
Location: Tasmania now, USA/Canada/Alaska in April
Posts: 2,472
There is usually a check valve in the line somewhere as well as a vacuum breaker so maybe the checkvalve has collapsed and blocking the flow. It happens on the check valves on HWS and on the mains inlet fitting so maybe does the same on the flush line.

Tony Lee - International Grey Nomad. Picasa Album - Travel Map
RVs. USA - Airstream Cutter; in Australia - MC8 40' DIY Coach conversion & OKA 4x4 MH; in Germany - Hobby Class C; in S America - F350 with 2500 10.6 Bigfoot camper
Tony Lee is offline   Reply With Quote
Old 03-22-2017, 07:30 PM   #3
Senior Member
Join Date: Apr 2016
Location: Full Timers
Posts: 339
Also the tank end of the flush system is a spray head so a little crud or a frog or a large bug could plug it. I have plugged mind with ice that was inside the hose. I would start at the vacuum breaker as it is the easiest to repair.
Dave & Sheryl Rambeau
2011 Itasca Meridian 39'
Rambeau is offline   Reply With Quote
Old 03-23-2017, 04:59 PM   #4
Senior Member
jeepfreak's Avatar
Join Date: Mar 2003
Location: Home is where we park it
Posts: 457
If your plumbing is like mine , the check valve and vacuum breaker are under the bathroom sink. You could start there by loosening the bottom connection and see if you have water there , then work your way to the other end.
2007 Allegro 34wa .WH w20 8.1 6speed. 2020 Jeep Gladiator Rubicon Toad.
jeepfreak is offline   Reply With Quote
Old 03-24-2017, 04:03 PM   #5
Join Date: Feb 2013
Posts: 30
Thanks for the tips, guys. I am due to return home within the next few days, and will use your info to attempt to get it working again. Will report back if/when I find/fix the problem. Much appreciated.
jacksonmacd is offline   Reply With Quote
Old 05-29-2017, 01:16 PM   #6
Join Date: Feb 2013
Posts: 30
Finally got around to fixing the problem. There is a check valve installed on the line and located under the secondary lavatory sink. Removed the valve, jostled it to ensure nothing was stuck and replaced it. Worked perfectly afterwards.

Thanks for the tips.
jacksonmacd is offline   Reply With Quote
Old 05-31-2017, 02:41 PM   #7
Join Date: Jul 2012
Posts: 84
black tank flush

Have a similar problem. No srpraying. Purchased a new check valve ($100), replaced it.........Nothing, nada!!

kayla44 is offline   Reply With Quote

allegro, black tank, tank

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
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
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Plugged up black tank flush valve tdyltc46 Class A Motorhome Discussions 11 09-25-2016 08:22 PM
2008 Allegro 34TGA Questions Paussie6 Tiffin Owner's Forum 2 08-25-2013 08:20 AM
Thinking of buying 2008 Tiffin Allegro 34TGA Paussie6 Tiffin Owner's Forum 6 08-18-2013 06:39 AM
Black tank auto flush plugged srrv Class A Motorhome Discussions 13 02-01-2012 06:59 AM
2008 Allegro 34TGA Rick Johnson Tiffin Owner's Forum 3 10-10-2010 07:43 PM

» Featured Campgrounds

Reviews provided by

Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -6. The time now is 07:57 AM.

Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2019, vBulletin Solutions, Inc.