A little physics problem

Education comes in many forms. I’ve been through the halls of academia and earned a Masters degree which has served me very little other than looking good on the resume. Most of the really useful stuff I’ve learned has been through the hands-on, just get in there and figure it out approach. This is one of those things that I was fortunate to have been gifted in and have, as a result, accumulated a lot knowledge of how and why things work the way they do. I suppose it was a natural thing that I was drawn to the Engineering field and in particular Systems Engineering which tends to focus on how a multitude of smaller bits are put together to accomplish the successful operation of a complete “system”. All of this is a prelude to discussing a learning situation I encountered the other night.

Problem: If you have a 50 gallon fresh water tank in your rig, and you fill it up before heading out to the forest, how much water will be left after three days of use? Well, obviously that depends on your daily usage which will be determined by how frugal you are with the water. Because we are veteran campers we know how to conserve water and make it last. Therefore, I was quite pleased when I checked the tank indicators several times and was rewarded with a “still full” status. By the third day however, I was beginning to get a little suspicious of this report. While we are frugal, we still have been using enough water that it should be reflected in the tank status. Perhaps, I thought, the float is stuck. Although, I couldn’t think of any reason why it should be as it had been reporting Empty all of the time before (which it was).

Now consider this is our first “dry camping” event, e.g, not hooked up to city water and electricity like we have been previously in public campgrounds. These events are where you get “learning experiences” which must be faced and conquered otherwise you might as well just live in an apartment and call the landlord every time something stops working. So, around 10pm or so, as we were getting ready to retire for the night, I noticed the water pump started running and did not shut off after a few moments per its normal behavior. This is bad because you can burn out the water pump if it runs too long with no water to pump. A quick look outside in the plumbing compartment confirmed that there was insufficient water in the line for it to operate. So, I shut off the pump too prevent damage.

How could this be? The tank indicator still registers as Full. There is simply no way we could have used up 50 gallons of water in a few days and I’ve not seen any sign of leakage. It’s really a very basic “system”; it has a fill spout with a stopper to prevent water from sloshing out when traveling down the road, a 50 gallon holding tank, a monitoring gauge, a water pump, and water lines to the faucet.
Water Fill PortTank Monitoring Panel
Water Pump I decided to tackle the problem in the morning but as I was laying in bed a probable solution occurred to me. Do you know what it was?
What occurred to me was that the stopper in the fill spout might be doing its job a little too well. Assuming it created an airtight seal, then as the water was pulled from the tank by the pump the resulting empty space in the tank would become a ‘vacuum’ pulling the water in the opposite direction. This would eventually become more than the pump could overcome and even though there was still plenty of water in the tank it could not pull it out. Satisfied that I had a possible solution I went to sleep.

A better way to campThe following morning I went out and opened the door to the fill spout. With a pair of pliers and a small screwdriver to slip alongside the stopper I released it with a very satisfying “whoosh” of air entering the tank. I then stowed the stopper in a more friendly position and went back inside. Sure enough, the tank indicator was now indicating half full and the pump shut itself off a few moments after being turned on and re-pressurizing the water lines. Problem solved, new experience gained, and one more thing to add to the checklist.

2 thoughts on “A little physics problem

  1. Nice work Sherlock!

    It would have received a swift kick from me..which probably wouldn’t have solved anything. Your approach was much more effective. 😉

    Love you guys!

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