Actual / Measured Tank Capacities on 2020 Elite II

[NCeagle]

I was sanitizing my holding tanks yesterday and decided to measure the actual amounts of water I can store/use in various situations.  Here's what I found:

- Fresh water tank - I can fit 28 gallons in the tank before it starts to overflow.  The pump can pull all 28 gallons from the tank with the last few gallons requiring a nose high Ollie.  Documentation says this tank's capacity is 30 gallons.

- Grey water tank - this tank holds 30 gallons before it's full.  Documentation says this tank is 32.5 gallons.

- Black water tank - this tank holds 15 gallons before full.  The documentation says this tank is supposed to hold 18.5 gallons (note that the tank has "15 US Gallons" stamped right on it).

So, it seems that in real life, each tank holds about 2 gallons short of it's capacity.  Not a huge problem, but worth noting if you are dry camping and trying to plan water usage carefully.

 

[Overland]

When I tested my fresh tank capacity, I was able to get just about 30 out of it.  31.5, actually, but I have a 2 gallon pressure tank.  So there's a half gallon missing in there between the fresh and pressure tanks, and I'm ok with that. I can dump all of that into the grey tank, plus another half gallon before I get water standing in the shower.  Though depending on how the trailer sits, I may have to 'burp' the grey tank at some point to get the air out, by rocking the trailer back and forth. (Still not sure what's going on there, but obviously the vent doesn't always vent.)

Since I cut my black tank in two and pulled it out, its capacity is zero.   Or infinite, depending on your perspective.  

You might try fiddling with the pickup tube in the fresh tank - it may not be all the way down.  

It probably goes without saying, but I'll say it anyway: don't trust any number on the tank monitor.  If you want to get a true idea of your tank capacity, you've either got to measure what you put in, or fill it up and then measure what you get out.  Which sounds like what you did.

Just as an FYI, here's a chart that I made for my tanks to give me a better idea of what's actually in the tanks vs what's on the display.  It won't be of use to anyone else, since every sensor will be a bit different.  Actually, I've found that it's not of any use to me either, since these numbers aren't reproducible.  But at least it's good evidence of how much error the tank monitor can show at times.  

Edited March 22, 2021 by Overland

[topgun2]

3 hours ago, Overland said:

Or infinite, depending on your perspective.  

Please let us know what the results are when YOU test this! 😁🙈🧻

[Overland]

15 minutes ago, topgun2 said:

Please let us know what the results are when YOU test this! 😁🙈🧻

[NCeagle]

3 hours ago, Overland said:

When I tested my fresh tank capacity, I was able to get just about 30 out of it.  31.5, actually, but I have a 2 gallon pressure tank.  So there's a half gallon missing in there between the fresh and pressure tanks, and I'm ok with that. I can dump all of that into the grey tank, plus another half gallon before I get water standing in the shower.  Though depending on how the trailer sits, I may have to 'burp' the grey tank at some point to get the air out, by rocking the trailer back and forth. (Still not sure what's going on there, but obviously the vent doesn't always vent.)

Since I cut my black tank in two and pulled it out, its capacity is zero.   Or infinite, depending on your perspective.  

You might try fiddling with the pickup tube in the fresh tank - it may not be all the way down.  

It probably goes without saying, but I'll say it anyway: don't trust any number on the tank monitor.  If you want to get a true idea of your tank capacity, you've either got to measure what you put in, or fill it up and then measure what you get out.  Which sounds like what you did.

Just as an FYI, here's a chart that I made for my tanks to give me a better idea of what's actually in the tanks vs what's on the display.  It won't be of use to anyone else, since every sensor will be a bit different.  Actually, I've found that it's not of any use to me either, since these numbers aren't reproducible.  But at least it's good evidence of how much error the tank monitor can show at times.  

Wow, thanks for sharing this Overland.  I did a similar thing when I was filling my tanks, but I used 5 gallon increments instead of 2 gallons.  I also found the SeeLevel readings to be all over the place and not of much use.  I heard lots of gurgling and had to shake the trailer around to get the air out of my grey tank too.

So you are definitely doing much better than I can do at the moment.  My 2020 owners manual says the fresh tank capacity is 30 gallons, the grey tank capacity is 32.5 gallons, and the black tank capacity is 18.5 gallons.  I'm going to try again and be much more precise in my measuring.

The real bummer is the grey water is our limiting camping factor at the moment and now that I've got an easy way to use my black tank for grey water I'm not able to use 6 gallons of grey capacity (2.5 gallons in my grey tank and 3.5 gallons in my black tank).  I opened a case on my black tank.  It really "stinks" (pun intended) that my black tank is only 15 gallons and it's supposed to be 18.5.  😞  I wonder how many other 15 gallon black tanks are out there.

Edited March 22, 2021 by NCeagle

[Mcb]

My black water tank is the same as yours.. I’ve wondered about the other 3.5 gallons of “of capacity “ as well.. I don’t think there is that much volume  between the tank and black water valve... 

[Rivernerd]

NCEagle:

Good catch.  It appears that Oliver noted your post highlighting the 18.5 gallon vs. 15 gallon discrepancy.  I have a 2022 on order, so after reading your post, I checked the specs for the 2022 Elite II: 

15 Gal. Design Capacity Black Water Tank with pressure flushing system for the Tank

Standard

So, maybe thanks to you, new buyers like me are on notice that they are getting only 15 gallons, and maybe less, depending on the difference between actual and "design" capacity.

 

 

[Mike and Carol]

37 minutes ago, Rivernerd said:

 

15 Gal. Design Capacity Black Water Tank with pressure flushing system for the Tank

Standard

So, maybe thanks to you, new buyers like me are on notice that they are getting only 15 gallons, and maybe less, depending on the difference between actual and "design" capacity.

Wish it was more.  It’s our limiting factor when boondocking. 

[Steph and Dud B]

16 minutes ago, Mike and Carol said:

It’s our limiting factor when boondocking. 

How many days can you usually go before needing to dump the black tank?

[Mike and Carol]

15 minutes ago, Steph and Dud B said:

How many days can you usually go before needing to dump the black tank?

If we have no other option (vault toilet or other) we can stretch it out to 4 maybe 5 days.

[SeaDawg]

I think the "design capacity" in the older trailers  included the volume contained in the pipe between the valve and toilet. That can be considerable, depending on where the valve is/was. I'm pretty sure we get an extra 3 to 4 gallons in our older Ollie, in the pipe. The math isn't that difficult,  just never had to figure it out.

We dump when we can, use cg facilities when available, including pit toilets,  and never been a problem for us. Except for when we are on extended stay, at  our camping property, we don't tend to stay in one place more than a few days. Then, it's off to new sights.

 

 

 

[topgun2]

16 hours ago, Steph and Dud B said:

How many days can you usually go before needing to dump the black tank?

In addition to SeaDawg's suggestions above on places to "go", there are always the use of a portable waste tank - I use a small size that is reasonably easy to handle (i.e. when full I can still pick it up to dump in a pit or regular toilet) - or, something like "wag" bags (plastic bags with dry chemicals in the bottom) for waste disposal like THESE.

In over 25 years of RVing I've never had an issue with "going".

[Steph and Dud B]

14 hours ago, SeaDawg said:

Except for when we are on extended stay, at  our camping property, we don't tend to stay in one place more than a few days. Then, it's off to new sights.

This is what we hope to do as well and why we chose an Ollie. When retired, we want to do more extended trips.