Water System Basics, Pt 1
Clean water; the cornerstone of most modern homes. In your house, the water probably comes from either a well or a municipal connection. Both are usually reliable sources of drinking water. When traveling, however, our home is on the road with us. We need to bring everything, including our sh*t, with us.
How do you determine how much to bring?
How do you filter and ensure it is safe to drink and cook with?
Do I have to worry about freezing?
How will I know when my tank gets close to empty?
How do I connect to the tank now?
These were all things I had to consider when designing the water tank for the system; one of the cornerstones of living independently.
Sizing the Water Tank
Our trailer has two main fixtures: the sink faucet (4.75 GPM) and the shower head (1.5 GPM). These flow rates determine how much water we would use within 1-minute of leaving them on. It goes by quickly!
Plotting our activities per fixture we could accurately guesstimate our daily consumption and determine how many days we could be independent. Working in liters made some of the math a bit easier to do. Later converting the units back.
| Consumption Calculator | ||||
|---|---|---|---|---|
| Fixture | Rate (gpm) | Rate (Lpm) | Qty/day (min/day) | Amount (L) |
| Sink | 4.75 | 17.98 | 0.50 | 8.99 |
| Tea/Coffee | 0.80 | |||
| Drinking | 8.00 | |||
| Cooking | 0.50 | |||
| Dishes | 2.00 | |||
| Teeth | 0.00 | |||
| Shower | 1.50 | 5.68 | 5.00 | 28.39 |
| Exterior Hose | 0.00 | |||
| Reserve | 1.00 |
With a total of 50-liters/day or about 13-gallons, we figured we would like to be independent for around 3 days before needing to fill up again. This conclusion alone may raise a few issues:
How we will fill up between days?
What about weight?
Is sloshing going to be a problem?
All of these questions are answered later on.
But let’s stick with what we know right now, 13-gal over 3 days, that’s at least 39-gallon tank. But what dimensions can that even be?
I knew I wanted to put the tank within the galley counter since it was going to be pretty long, whether or not it protruded into the bench, could be later determined.
The width from side to side had to be less than 16-inches: from the rear of the inside toe-kick to the outside port wall.
The height had to be around 18-inches: the height of the benches around the dinette.
| 50 | Liter / day | |
|---|---|---|
| 3 | Days w/o H20 | |
| 149 | Tank (L) | |
| 39 | Tank (gal) | 1L = 3.7854 gal |
| 5.3 | Tank (ft^3) | 1gal = 7.48052ft^3 |
| 9095 | Tank (in^3) | 1ft^3 = 1,728in^3 |
| 16 | Width (in), counter-toe kick | |
| 17 | Height (in), bench | |
| 33.4 | Length (in) | |
| 328 | Weight (lb) | 1gal = 8.34# |
Converting the volume from LITERS (L) to GALLONS (gal) to CUBIC FEET (ft^3) to CUBIC INCHES (in^3) allowed me to conceptualize the amount of water needed for 3 days in terms of INCHES. Taking away one side of the tank at a time, I determined how long of a tank I would need to buy. With these rough dimensions, I set out on the internet to find a tank within these specifications.
Fitting the 40-gallon tank within the roughed-out galley cabinet/counter.
Fortunately, this seems to be a common tank size. That is good for me since I would not have to wait on an expensive custom order to arrive.
Onto the next issues at hand. Sloshing.
Tank Sloshing
Newton’s first law of motion: an object in motion will stay in motion until acted upon by an outside force.
When the trailer is in motion, everything in that trailer is moving at the same speed. This includes the jar of peanut butter, the dirty dishes, and most importantly, the water within the water tank. The only issue: when the trailer stops, the water within the tank wants to keep moving! The water has too much inertia.
To prevent this phenomenon from turning catastrophic, industries have come up with a technique/system called baffles. Marine vessels use these in their fuel or ballast storage, liquid-carrying 18-wheelers, have these within their trailer, and any other number of transport vessels may employ this technique.
Inertial effects of liquid within a vessel.
Without some type of internal baffle in the system, the mass of the liquid within a vessel can rock, sway, or even tip the vessel and anything the vessel is attached to. This becomes a huge safety concern.
At 40-gallons, that’s over 300-pounds of water potentially moving around within the tank. Especially if the tank is anywhere between full and empty.
The baffles themselves can be physically part of the tank walls or a large enough geometric shape (in the right quantity) that float freely in the tank. With the latter, the right shape tends towards spherical for ease of installation through a circular access hole and volume/constructability characteristics. For industry, baffle balls can start as large as 24-inches. This will not work for our purposes, since my access port is only going to be about 4-inches in diameter.
Wiffle balls. They are about the same size as a baseball and have slots or holes inside of them for airflow (maybe? never played.) These became the perfect solution to the problem.
With about 80 wiffle balls within the tank, they fill to about two thirds the total volume. I figured that the sloshing effects can be dampened with at least two full layers of balls on the surface of the water, and any more than that will hurt.
Go find the next article on water systems or explore other systems!
