RV HOLDING TANKS
Rule #1: Think before you panic!
A recent call I made on a customer reinforces the adage that one should
first think things through with rv holding tank problems before hitting the panic button. This individual recently
purchased a used 5th wheel and was living in it. One of the first things he
told me was that he had experience with rv's...but I'm not so sure.
Once he had possession of the 5th wheel and was living in it he discovered
his black tank dump valve was stuck open. He thought this was better than
having it stuck shut, but thats not true either.
Any experienced rv'er with a motorhome, travel trailer, or 5th wheel knows the
black tank should only be used with the dump valve CLOSED so that liquids and solids are together.
If there are no liquids in the black rv holding tank this obviously leaves only solids which eventually will lead to black tank flush problems. I was there to replace his black tank dump valve and once
I was into the job I discovered I didn't have the correct dump valve to complete the job
so I left everthing as I had found it...valve open as he had been using it. By mid afternoon he called the office with what he thought was a problem, of course caused by no one else
than "yours truly".
I called him for the specifics of his problem and this is what he told me.
"My toilets plugged so you must have done something
to cause this."
I responded that I left the black tank valve "open" just as I had found it.
I then calmly asked him this question:
Are you telling me you filled your black rv holding tank since I left you?
(He was assuming his tank must be full)
After being presented with this question and pondering over it he knew this
likely was not the case. All he knew was that his toilet was plugged. (Yuk!)
I called on him later in the day and found the toilet full to the brim. I turned
the water off, flushed the toilet and to his chagrin it flushed normally. How
about that, I thought!
Rule #2: Toilets with angled pipe to the black tank
require lots of water to properly flush.
I've also learned this the hard way with our Holiday Rambler 5th wheel. Angled
pipes from the toilet to the holding tank plug easily but the good news is its
easy to diagnose. Here's some pointers:
- if you notice any change in the flushing action of the water
in the bowl when flushing you know you either have a partial
obstruction in the pipe under the toilet OR your tank is full.
" Its one or the other." (A total or partial obstruction will cause
the water to bubble up rather than immediately flush as
- once an abnormality is noticed in flushing you should first
verify the fill level of the tank. (This is not always as easy as
checking the black tank monitor because they rarely perform
- After either dumping the tank or verifying it is not full, flush the
toilet, hold it open and let it fill at least half way with water. Yes
this is scarey but you're probably in this situation anyway after
ignoring the warning signs I've just listed. Now with ample water
in the bowl use a plunger and attempt to clear the plugged pipe.
Normally this proceedure will be successful (if the tank is not full).
If it is not successful and the tank is not full most likely this problem
has been developing and growing worse with time in an rv that is
not used on a regular basis, and guess what? This blockage has
had time to sit and dry out...only exacerbating the problem. Your
option now is to let it sit and add an enviromentally safe substance
that will hopefully break down the blockage. If time is of the essence
someone (like me) is going to have to try to ream the blockage
out or the last resort, tear things apart.
The moral of the story is as this report started out. Think before you panic. My customer
could have saved himself an unnecessary service call because it was highly unlikely
that his tank was full. Had he thought this out he could have determined he most likely
only had a blockage and he could have attempted to clear it out.
RV holding tank problems can be exasperating... but think before you leap. In most cases things probably aren't as bad as you may think.
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