Blow, blow . . . suck is just a figure of speech!
This post is about the science of siphons.
Mexico is a funny sort of place about its water supplies. The marina here does not have potable water. The Grand Wyndham Isla Navidad resort hotel also does not have potable water. For a host of reasons, Mexicans, in general, do not trust their water supplies. Everyone, and I mean everyone, uses bottled water. If you order a glass of water in a restaurant, you get a bottle (unopened) of purified water. I tested the water in the marina’s system and it tests fine according to the tester for our RO desalinator. Which, in reality, just means it is not salty; it does not mean it is safe to drink from because of a host of other things. But if a five-star resort says its water is not drinkable, I will believe them.
Our water taxi was late this morning, so we missed church and stayed on the boat instead. As with all things cruising, there is never a shortage of work to do. We chose to use the time to fill Spiritus’ water tanks. We use about three gallons a day of fresh potable water, so we have to fill our 55 gallon tank more or less every two weeks. Yes, I did the math … we usually have ten gallons or so left in the tank when we refill it.
Spiritus’ water holding tanks are built into the keel and use the space that the builder saved when they used lead, instead of iron, to ballast the boat. The fill-point for the tanks is in the main cabin inside the boat. You access it by lifting a floor panel. This presents a couple of problems when filling the boat’s potable-water storage. The problems are getting the water downstairs into the cabin and the mess, which pouring multiple five-gallon bottles can make. There is always spillage.
We noticed Sven on Senta II using a method I had not seen. At first, I didn’t pay any attention because it was a simple siphon. Duh! Remember he and his wife Nancy really are rocket scientists in real life. When I looked back a second time, I noticed he simply thrust the hose into the bottle, made a seal with his fingers, and put his mouth to his hand, and …. blew!
Miraculously, as I watched, the bottle emptied itself.
Now, this will give my age away slightly, if the accompanying pictures don’t. I remember siphons as things that left your mouth full of gasoline or diesel or God-knows-what. This is because you sucked the fluid up to till it started to run down whatever hose you had in your mouth and you deftly removed the hose from your mouth and put it in whatever container you were trying to fill–all the while, desperately attempting not to gag, retch, or swallow in the process.
I had Sven show me exactly what he was doing and had one of those moments of epiphany … “duh … boy am I dumb” moment as I watched. In Arkansas, where I grew up, and especially in my family, the feeling you were suddenly dumb for not knowing something, is what the rest of the world describes as an epiphany. He told me later that one of the local fishermen in a panga had shown him the technique.
You simply open the bottle and
(1) with bottle sitting on floor,
(2) insert hose (in our case, a three-and-a-half foot long, inch-and-a-half diameter, clear water line hose)
(3) wrap two fingers around the hose at the top of the bottle
(4) take a deep breath
(5) make a seal with your lips
(6) exhale forcefully (blow . . . this pressurizes the bottle and forces water up over the top of the loop initiating the siphon effect)
(7) watch a five gallon, 30 pound bottle empty in about 70 seconds.
Repeat ’till all the bottles sit empty on the dock. Takes perhaps 15 minutes, or so.
We are good for another two weeks.
So, the gist of the posting is that everything we know about siphons is wrong headed. The panga operators have it right. Viva Mexico!
We have a water maker/ desalinator on board. It is a good one but mostly used on passages for a couple of reasons. It takes an hour to make a gallon-and-a-half of water. This means a constant drain on the batteries so it is only used when under motor power. We could use it at the dock but the water quality of the lagoon here and especially of the water near the docks is at times very, very questionable. (Read your water-maker hand book for cautions …. it is meant to be used in open water … even our step filtering system for cruising would be stressed by the water here in the marina.)
Finally, we looked at what using bottled water for the summer would cost and decided to save the wear on this expensive piece of equipment. We pickled it ’till the sailing season is back.
The only thing we are going to change about this siphon system is to get a 14 foot long piece of wate- hose so the tank can be filled from the deck. This would take away the necessity of lifting and carrying 8-10 bottles that weigh 30 pounds each up and down the hatchway.
And, yes, in the background, behind the now-empty bottles, is two pots of pork roast being solar cooked to make arrachara or Mexican pulled-pork tacos. When it stops raining, we cook with solar.