[VAC] Blackwater Tank Removal and Repair

["Harvey Barlow" <harveybarlow@xxxxxxxxxxxxx>]

Chris,

It is a common problem.  Not much fun but manageable by the average person
who can use basic hand tools.

I have done two recently, my daughter's '72-27' and my own '66-22'.  A list
member recently advised that he had an estimate from an RV repair shop for
over $800 for repairing his and that was not including the probably required
new black water tank, new holding tank cover, and assorted parts that will
probably be required.

Here is a brief summary of the steps required:

1) Remove the toilet which should have two 1/2" nuts holding it to the
floor, front and back.  Remove the fresh water flush connection from the
toilet of course.  You should be able to locate the front nut by depressing
the flush pedal and looking back inside.  There may be a push out plug on
the top rear of the toilet which will permit access to the rear nut with a
12" extension and socket.  If it is a standard Thetford toilet you can
contact Thetford for a print, or visit a local RV store to visually inspect
one.  Experienced RV mechanics on the list can tell you more detail about
the toilet.

2( Remove the toilet flange by rotating clockwise after soaking with Liquid
Wrench at the junction with the holding tank if you can get to it.  (The
toilet flange is installed from above through the bathroom floor after the
holding tank is in place.  The holding tank has a threaded fitting which the
toilet flange screws into.  It "should" be removable with Liquid Wrench.)
If you accidentally break the tank or tank flange or find breaking it is
required in order to separate them, don't despair.  The most likely cause of
sewer odor and a very common problem is a broken tank.  Chances are you are
going to be purchasing a replacement or having your tank repaired anyway.

3)  Disconnect the holding tank vent stack from the tank.  It may have a
slip joint with clamp or you may have to cut with a hacksaw then reinstall
using a PVC or ABS collar.

4)  Remove the front and rear angle iron tank supports.

5)  Drop the holding tank cover.  You will have to remove the tank cover
patches which close the opening around the dump valve assembly in order to
drop the tank.

6)  Remove the holding tank dump valve assembly by removing the four
stainless 1/4 20 screws and nuts that hold the two halves of the dump valve
assembly together.

7)  Some trailers may have wood screws penetrating the folded outer edge of
the holding tank cover screwed into the plywood floor of the rear
compartment.  If yours does, the screws must be removed to remove the tank
cover.  I don't think yours does.

8)  You will most likely discover that the top of your holding tank is
broken.  Most are molded of polyethylene plastic which nothing will adhere
to very well.  A list member, Nick Novia, knows an industrial plastics
company in CT who will hot air weld the tanks for approximately $100.  I and
others can provide sources from which to order a replacement tank.

9)  Retain your holding tank cover for a pattern and have any good sheet
metal shop bend a replacement.

10)  Throw away the rusted angle irons.  They are made of standard 1 1/4"
angle that can be purchased from any steel supply company or Home
Improvement store, cut to length, primed, and painted.

More questions?  Don't hesitate to ask.

Good luck on your tank replacement.

Harvey Barlow
Lubbock, TX
WBCCI # 1171, WDCU, VAC