Silverbacks

A number of years ago I bought a toy hauler that was supposed to have a 75 gallon water tank, not including the water heater. The first couple of times I used it, it never seemed like I had any where near that much water available.
When I got underneath the trailer and looked at the tank I found that the vent hose was located on the side of the tank, about an inch below the top of the tank, and the pump pickup line was also located on the side of the tank, about an inch above the bottom of the tank. Using the area of the bottom (and top) of the tank, I calculated that one inch of depth in the tank would hold about 10 gallons of water. Turned out that when the tank was "full", at least 10 gallons of tank capacity went out the vent hose, and the last 10 gallons in the tank couldn't be pumped out, so I had only 55 gallons of usable water from a 75 gallon tank.
I did have the dealer move the pump pickup fitting to the bottom of the tank, so I was able to get the last 10 gallons from the tank. Couldn't do anything about the upper 10 gallons without dropping the tank.

the overflow hoses are likely too low.

Used the water meter two times. Then filled five gallon pails, just under ten pails to overflow . So there are my measuring cups.

I always carried extra water when boon docking in my 2013 Silverback. I don't think it held over 45 gallons.

Brockinfla wrote:
How are you measuring the 46 gallons you're claiming to get into the tank?

My guess is one of these:


Pretty inexpensive. Makes me want to order one.
Water Meter on Amazon

How are you measuring the 46 gallons you're claiming to get into the tank?

Are you sure your measuring cup was accurate?

Got it. But it seems that 66 gal should be 66 gal. Had a HitchHiker that said 70 Gal FW. That's what it was when filled, no water heater, no water lines, no what ever. That's what the tank size was. Thanks all for the reply's.

Sounds to me like you're in the ballpark. FW capacity usually includes the WH, so there is 10 gal of it. Then the tank manufacturer places a size rating on their product which is completely full, no air at the top. They might even ignore the radius in the corners. Then if the fill and vent ports are in the side, as they usually are, you cannot completely fill the tank. Add a little in all the plumbing lines, and you end up with much less useful capacity. It is even possible the outlet port is in the side, which means it will not fully drain.

FW capacity is important to me, and if it is to you, I would suggest you get eyes on that tank. Note where the inlet and outlets are plumbed, and when full does it still have a lot of air at the top. FW tanks are usually translucent, so you can see the level pretty easy if you hold a flashlight against the tank wall. I cut a window flap in my corroplast so that I could easily check on the tank.

tko9900 wrote:
All the brochures dating back to at least 2010 to 2016 all say between 64 to 67 gal. I am sure the tank is empty, raised the front up to make sure. Hope the holding tanks are what they say they are. Not a big deal but lets get it right year after year of brochures. My unit is a 2013.

Did you drain via the low-point drains? If the WH is 10 gal, that means the main tank is, or should be 50. Given the "interpretation" that most mfrs put on tank size, I can see that 46 = 50 to them. :S

Lyle