BLUF: Here's most of the system:
In response to a thread in the main forum, here is my system for quickly and easily filling the water tank from inside the van. As your water containers may differ, your required component may differ slightly.
I use plastic garden hose quick disconnects. I'm using Melnor brand (home depot???) right now, but you could also use "Back Yard" brand (OSH), and I believe they are interchangeable. For instance, this starter kit would get you most of the way there (it would cover the tank, the hose extension, and the 5 gal container; you'd just have to get a F hose repair component):
Nomenclature: For the "quick disconnects" I will use QD(F) or QD(M) to refer to the male or female type. For the "garden hose" side of the connector, I will use H(F) or H(M) for the female or male type. Thus, if I write QD(M)-H(F), that means it's a connector that has a male quick disconnect on one side and a female hose attachment on the other. Confused yet? This is important if you add more components, as you'll end up needed to mix different genders.
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FILL TANK
To keep this on there, you'll either need to drill out a hole in your door as the connection will stick out, or remove the door entirely. I did the latter; that way I can always check on the water level.
On the tank connection: QD(F)-H(F). I chose one of the QD's with a one-way water valve. However, unless the pressure is high, you'll still need to cap this.
On the hanging cap that comes with the water tank: QD(M)-H(M)
Now you can snap that cap in and out of your water tank to open and close it quickly and easily.
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4' HOSE EXTENSION
SMB provided me with a ~4' garden hose.
1 x QD(M)-H(M)
1 x QD(F)-H(F)
Now your hose will quick connect into your water tank.
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5 GAL JUG
Many people seem to have these, but you may need something else depending upon your fill container. The following is what I used:
Jug end: Plastic garden hose repair insert (F) plus QD(M)-H(M). See photo.
Filling: connect, tip, and fill.
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MSR DROMEDARY BAG
As the Badgers noted in their blog, showering from the sink/shower wand sucks. Best to fill an MSR Dromedary bag-shower (5L size? Don't recall, but it's the largest one they sell) with hot water, hang it from the ceiling, and use that. You save water, and don't get hot/cold blasts. Since we have this, we also use it to fill. I simply cut the shower hose and inserted connectors.
1 x garden hose repair piece (M)
1 x garden hose repair piece (F)
1 x QD(M)-H(F)
1 x QD(F)-H(M)
NOTE: the above two items could be mixed the other way around, F and M. Doesn't matter really, since you're splicing in to the Dromedary hose in the middle anyway.
And fill, either directly if you left enough hose, or if the top is popped, use the garden hose as an extension. Easy enough to do, since it's all quick disconnects!
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FAUCET CONNECTION
This is getting extreme and most won't need this, but in blistering cold conditions, with a QD(M) connector on the faucet, we can recirculate warm water into our water tank and lines to help prevent freezing. Note: Do NOT circulate hot water into the tank; the pump cannot take water over 120F I believe or you'll ruin it.
1 x QD(M)-H(F)
1 x Faucet to Garden Hose connection adapter (any hardware store)
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FILLING YOUR JUG FROM A SINK:
I don't have a pic of it, but I have connected a funnel to a QD(F) via a (M) hose repair piece. This allows me to put the 5 gal container on the floor, attach the 4' hose, and attach the funnel for filling easily from any sink. Fast and easy...
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FILLING YOUR WATER TANK FROM A JERRY CAN:
I'd get a "Super Siphon" (do a google search) and put a QD(M) on the other end. This will allow you to siphon from the hard Jerry Can directly into your tank via the QD system.
Come to think of it, if your hose is long enough, and you keep your Jerry Cans on the back bumper, you could just prop the can up on top of the box/other Jerry Cans, and siphon from there into the tank, thus not having to lug the can all the way inside the van. You could leave the hose running along the inside, and have it almost ready to go every time.
PPS: If you're REALLY handy/insane, you could take your water tank out (or order a new one) and get a coupling/input added on the back side (facing the rear of the van). With a QD (or not), now you could have a fill hose permanently attached to the back of the tank, and routed to the rear of the van. Filling from Jerry can would be as easy as: lift Jerry Can onto others (to raise it), uncap hose end and snap on super siphon, and siphon. If someone does the Jerry Can/Super Siphon mod, post pics here please for when I do it...