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Black tank

Yahoo Message Number: 35
We had an interesting and annoying experience today. We departed
Waterford Hills Michigan with our tank indicators showing black tank
2/3rds (and figured it was likely half at most) and grey showing 1/3.
When we got home the grey was still showing 1/3 but the black showed
FULL. That rather surprised me. So, I flushed and held it open (pump
off so no more fluids going in) and it looked like the tank was in fact
full.

I'd thought about dumping before we headed home but DW wondered why
since we had two trips (arrive Friday and depart Monday) to the same
place and dumped after the 2nd and both tanks seemed far from full.

Now I'm wondering if there is an elbow under the toilet. When I think
of where the tank appears to be located, I don't think it is directly
under the toilet in the Greyhawk. Anyone have any ideas. I don't like
the idea of sitting with a full black tank (if that is the case) and now
I may have to look around and see where I can dump it.

This is now our 4th motorhome since 2003 and not one of them has had
tank indicators that were close to accurate.

Don
2007 Greyhawk on Kodiak

Re: Black tank

Reply #1
Yahoo Message Number: 36
After setting for a month. Both my tanks showed over 1/2 full. I knew
there was some water in both tanks but had been both dumped. Hooked up
the Shur-flo macerator pump and emptied both tanks into the dump line
I have in the backyard. Check the level again. Still 1/2 full. Hooked
up a water hose to the tornado flush on black tank. Turned water on
for about 5 minutes. Went inside and check tank level. It now
registered empty. Did same to gray tank. Both tanks now read empty.
The Tornado flush works great on both gray and black tank. Got mine at
Camping World.
http://www.campingworld.com/browse/products/index.cfm?prodID=4969&src=SRQB

Re: Black tank

Reply #2
Yahoo Message Number: 37
Interesting, thanks.

I have a black flush built in and when we dumped prior to leaving the track last month it said empty and stayed that way. I have a clear plastic segment at the valve and was surprised to see what was being flushed out.

This morning I went out and it now says only 2/3rds full. Kind of makes me think of a comment I heard from a tech - the sensors don't work well when they are wet? :) I guess the contents of the tank sloshed around during the drive home. Going to get the flashlight and take a look again.

Don

Re: Black tank

Reply #3
Yahoo Message Number: 38
Well, this afternoon it was down to a 1/3 full. I guess what Tim Deronne said about the sensors above the fluid level not working when they get wet is correct.

I had a look down into the tank and it is directly below. Sure looked like a shallow tank to me so I crawled underneath for a look. I don't now how deep it is but it might only be a foot deep. Given it is a 51 US gallon tank, I try to think of the room 10 5-gallon jerry cans would take up. Seems like a lot until I compute that that 51 gallons only takes up 6.817716 cubic feet. So it is very shallow and the sloshing would be significant.

Don


Re: Black tank

Reply #4
Yahoo Message Number: 66
The tanks are usually not deep at all. Just as an example... a
36"Wx54"Lx6.06"D tank would hold 51 gallons (length x width x hight /
231 (231 cubic inches to a gallon)).

The black tank sensors collect tissue paper, which holds moisture and
causes errant readings till the paper drys. Keeping the tank cleaned
out the best you can will ensure the most accurate reading. However,
I never trust the black tank gage.

Re: Black tank

Reply #5
Yahoo Message Number: 67
Yes, I made the calculations last month. (7.480511 gallons to one cubic foot) When I looked down into the tank it appeared it could be about 12 inches deep which it only has to be 2 ft x 3.41 ft x 1 ft deep - sure not very big. If it is only 6 inches deep then it is going to collect even more yet. We use the black flush system and the first time were surprised at the amount of tissue that did get washed out. Never saw this with our pusher - don't now why because its "external" sensors didn't work any better than the internals.

The next month we dumped before we left the track. Didn't show as empty. After we got home and it "dried" for a while, it showed empty. So, Tim deRonne was right about these sensors not working when they get "wet." :) Glad they don't make gas tanks.

Don

ps. My favourite site for weights and measures conversions is below. Provides just about any measure one will every need.

http://staff.library.adelaide.edu.au/sthomas/conv/