Fix a slow well cheaply (sorta) Part 1

[MJB]

If I recall my chemistry class notes correctly, /w3tcompact/icons/crazy.gif water actually reaches maximum density at about 39 degrees F. This, together with the warmth coming from the earth below the frostline, is why ponds and lakes freeze from the top down instead of the bottom up. When the water in a pond reaches this temperature a "thermal inversion" occurs where the water near the surface is the coldest water in the pond instead of the warmest. I still think you will be OK with the depth of your tank, especially if you have some snow cover on the ground when the weather is the coldest.

I love the smell of diesel in the morning.

 

[TWINKLE_TOES]

MJB,
I think your recall is pretty good/w3tcompact/icons/smile.gif
A question in a physics class "what is the temperature at the bottom of the lake when the lake freezes?" Answer 4 deg C.
Al

 

[patrickg]

Paul, I like your approach to the task. Thought I would inject a hopefuly helpful comment The temp underground baring unusual thermal activity (hot springs/guysers) varies essentially in a continum from a sort of average of the air temp with a sliding window of integration way under a day to a nearly perfect constant average of the surface temp at depths, depending on soil type and moisture, something like about 10 ft. or so (different authors claim different depths depending on what they are selling). The variation of temp on the surface is on the order of the magnitude of the delta T of the air. As you go deeper the delta T falls off rapidly and begins to loose daily variations and just show seasonal variations. At greater depths only climatic changes are felt (like global warming or an ice age. The temp of the water coming out of your well after it runs enough to cool the plumbing is approximately the deep earth temp for your area (real close to annual surface mean unless your pump is really inefficient and imparts a fair amount of heat to the water) Your statement regarding the constancy of the earth temp at shallow depths is innaccurate.

Over time, if you aren't there to consume water, the thermodynamics of the system will drive the system toward an equilibrium. As a first approximation, including some reasonable assumptions and worst case allowances consider the coldest surface temp expected and the frost depth. Linearly interpolate temperatures over that range. Say -20 at surface and say 32 at 42 inches down. (substitute best numbers for my rough approximation used to illustrate a pragmatic solution NOT generate THE answer for your situation. This gives 52 degrees over 42 inches. Part of your tank is in this "regime". Part of it is lower down where it is not so cold. Similarly estimate the temp lapse rate from 42 inches to the depth you think it becomes more or less constant. At that depth use the well water temp.

Now you have two contrary influences. One is heating the tank and one cooling it. The math is identical to balancing your check book. Heat can be added to the tank by soil below the frost line and subtracted by that above it. I would probably use one inch graduations since a calculator makes easy work of this.

This is an approximate method and certainly could be improved on with calculus but it isn't worth the brain strain for another 10% accuracy. If the final solution is that less heat is added by deeper ground than is taken away by shalower ground it will freeze. If not, it probably won't. If it is a tie or photo-finish I'd bury it deeper as the error in the assumptions and calculations probably are in the +/- 20% area. Oh yeah, I forgot to mention one of the assumptions, that the tank is approximately rectangular. Math is not all that more complex if you want to draw an approximately tank shaped figure using only vertical and horizontal lines (like pixilation). For a first guess sort of thing rectangle vs cylinder isn't that much different.

If you want to discuss this but feel it beyond the scope of interest or would take too much shared community bandwidth, send me a private message.

Patrick

 

[PaulT]

The pumptec controller

PaulT

 

[PaulT]

I continue the story in Part 2. Click on this link to go directly to part 2 now

PaulT

 

[PaulT]

Thanks for the thoughts on the cistern freezing (or not). I believe I will send an email to the engineer at Norwesco with a link to this thread and ask for a comment regarding freezing if I buried it according to their specs. I will post the response under part 1.

PaulT

 

[MarkV]

PaulT,

Great information and I thank you. Your assessment of our climatic conditions here in N. Georgia is right on. Patrick brings up information I feel is more applicable to your climate than mine. It would be a rare year when we could freeze a large volume of water. In my situation, this is a weekend house that we spend 3 days a week at, often with friends. For the most part, our well does all we need. When we have occasions that large volumes of water are needed, such as filling the hot tub (350 gal, takes about 1 hour), sediment will show in the water. Not often do we need to pull that much water at a time, but given our drought years of late, I do worry about our supply. If I were to upgrade our system, I would also like to add more pressure. It would seem that I could achieve this from the tank with the right pump set up. Would that be your take on controlling pressure?

MarkV

 

[Phred]

<blockquote><font size=1>In reply to:</font><hr>

Oh yeah, one more thing - algae and bacterial growth. I'm no expert on either (biology eludes me, too), but sunlight promotes the growth of BOTH in water tanks. Since cisterns have to have an air vent, you could create a great breeding ground for these critters.

<hr></blockquote>

Mark and Paul,

If you want to do an above ground system you can use a cholrinator or UV to kill the bugs. In the electronics industry we use a lot of very pure water and chlorine is not an option since it would contiminate the expensive pure water. General the water is purified and stored in large tanks. These tanks constantly circulate the water through a UV source that kills any bugs.

A chlorinator might be a cheaper way to go since the UV requires power. Although one could probably set one up to run off solar.

Fred

 

[patrickg]

Paul, This might not be such an appreciated comment B U T for the health of all users (and this is not a comment on your personal hygiene as what I am saying wouldn't change if you hadn't been in swimming in the tank) Chlorinate! With your circumstances, it will be a pain but for safety sake I strongly advise you to super-chlorinate the first batch of water. If wasting that much water (too much chlorine to drink in my estimation) doesn't sit well with you, put in an activated charcoal filter to pull out the chlorine at point of use. There is plenty of trained medical advice available here, maybe one of that "gang" will comment. The instructions on dilution etc is on the bleach bottle of Purex or whatever.

I don't think the risk is worth it to use this without an initial sterilization.

Patrick

 

[PaulT]

Patrick,

Wonderful observation. I also appreciate the affirmation of what I did. Because the tank sat exposed to hot summer sun for a week while I backfilled, I DID chlorinate the water before using. I found a site on the web that gave chlorine/water ratios for shocking water. I believe it amounted to about a pint for the 350-400 gallons I had accumulated. The basic rule of thumb is, if you can't smell it (reasonbly stongly), add more. While chlorine at that level won't hurt you, it is unpleasant to taste. Fortunately, I had designed my plumbing a few years ago with a separate line for drinking water to my kitchen faucet and icemaker/water dispenser in my fridge. The other house water goes through a water softener (which no longer works after sitting idle for 2 years due to lack of water for rinses/w3tcompact/icons/tongue.gif - but thats the next chapter of this story.)

The separate drinking water line first goes through an inline filter. I currently have (from memory, now) a .5 micron filter for odor, bacteria, turbidity, chlorine, etc (but NOT VOCs - that adds about $15/filter). I believe the chlorine shock saturated my filter, but I left one in there for about a week, then changed it out. Even though ti looked clean, by the time I changed it out flow was severly restricted due to the chlorine molecule saturation. I also stirred up a bit of iron sediment from existing piping (not from the well), so I am now on my 3rd filter since putting the new system into service the 1st week in August. Still a cheap price to pay for keeping my little ones from having GI problems.

The chlorine running through the other pipes cleaned out some of the scale that had accumulated, too!

PaulT