Fresh Water Capacity Force HD 37BH

[LTZ470]

Yes sir, agreed, in defense of Dynamax, there are many Class A's with MUCH less capacity...I'll definitely add another water tank to my XL when it is delivered, minimally, but probably an additional grey tank as well...

We like to dry camp for up to two weeks so we'll need the extra capacity...

[Jammer151]

Originally Posted by sconnors11

Sorry for the delayed update.

-I installed a 1.25" pipe plug in place of the overflow.
-Tank was completely drained, same procedure as before.
-Using the gravity fill outside the rig, was able to fill almost 1/2" higher (74.5 gallons)in level before the sound changed (water level rose above vent fitting) -I continued to fill for a bit more, but stopped when water started to mildly spit out. I honestly didn't feel comfortable taking a chance to pop a fitting off and get everything wet under the bed.

Ended up with the overall level 1" higher than before the plug was installed (77 gallons) It looked like there was another inch of air in the tank.
That additional inch should give another 5 gallons if filled. It looks like the tank might hold 81 or 82 gallons with no vapor space in the tank.

Now for the good news! I drove the rig to run an errand and there was no overflow sloshing! This is the first time I haven't left a snail trail after topping off the fresh water tank. Pretty stoked about that.

There isn't all that much to be gained in capacity by plugging the overflow, maybe 4 or 5 gallons, but the lack of slosh loss should save at least that amount. I think its probably a 8 to 10 gallon difference from fill-up to camp. That's worth the cost of a dollar plug and some PTFE tape and 15 minutes of effort.

It's still a bit of a hard pill to swallow that there's no way to get much more than 80 gallons into a "100 gallon" tank. I'm not sure about the accuracy of the meter I used, so I would encourage others to do their own testing. Maybe a factory test on an uninstalled tank? The numbers from testing align with the strapping chart calculations (~4.9 gallons per inch).

Please ask questions and comment with your own experiences.

Sean

Thanks Sean for doing this, this explains a lot. We were mentally set to use 20 less gallons than our last rig and when we ran low way before expected we couldn’t figure out why...now we know. It is disappointing as this was one of the selling points for us as we knew we would have to give up some capacity moving from a 5th wheel to a coach and I was happy when I found one where the difference was minimal, but with this discovery it is more than minimal. Still love the rig....

Brian, could y’all test on an uninstalled tank?

[bclemens]

Sent this over to engineering to take a look. We'll also look at running both the overflow and vent out the top...but that will require a new bed base design to add height to the bed.

[Jammer151]

Brian, any update?

[bclemens]

Not really. The tanks are labeled size, which is what everyone quotes. I have tasked them with figuring out how to change the vent and overflow to a top mount...which requires a higher bed which means redesigned bed base. At least to do it the right way.

[mookieblaylock]

Originally Posted by sconnors11

Sorry for the delayed update.

-I installed a 1.25" pipe plug in place of the overflow.
-Tank was completely drained, same procedure as before.
-Using the gravity fill outside the rig, was able to fill almost 1/2" higher (74.5 gallons)in level before the sound changed (water level rose above vent fitting) -I continued to fill for a bit more, but stopped when water started to mildly spit out. I honestly didn't feel comfortable taking a chance to pop a fitting off and get everything wet under the bed.

Ended up with the overall level 1" higher than before the plug was installed (77 gallons) It looked like there was another inch of air in the tank.
That additional inch should give another 5 gallons if filled. It looks like the tank might hold 81 or 82 gallons with no vapor space in the tank.

Now for the good news! I drove the rig to run an errand and there was no overflow sloshing! This is the first time I haven't left a snail trail after topping off the fresh water tank. Pretty stoked about that.

There isn't all that much to be gained in capacity by plugging the overflow, maybe 4 or 5 gallons, but the lack of slosh loss should save at least that amount. I think its probably a 8 to 10 gallon difference from fill-up to camp. That's worth the cost of a dollar plug and some PTFE tape and 15 minutes of effort.

It's still a bit of a hard pill to swallow that there's no way to get much more than 80 gallons into a "100 gallon" tank. I'm not sure about the accuracy of the meter I used, so I would encourage others to do their own testing. Maybe a factory test on an uninstalled tank? The numbers from testing align with the strapping chart calculations (~4.9 gallons per inch).

Please ask questions and comment with your own experiences.

Sean

We're preparing for a trip next week, and this has been on my todo list for quite some time. I added a thread taped 1-1/4" plug last night and was probably able to add the same extra amount of water you noted. Not having to worry about losing several gallons to sloshing out the overflow, though, will be outstanding.

Thanks for taking the time to document your findings!

JT