The wind is howling outside like a winter storm, but some day it's
going to warm up and I'll want to open my in-ground swimming pool. In
order to extend the season (I live in Maryland), I'm thinking about
either a solar blanket or a "pill". The former appear to be made out
of the same bubble wrap you see in packing, and require a reel to take
them off the pool. The latter is apparently a substance that slows
down evaporation, which presumably is the main form of head loss.
The pills are not supposed to be as efficient as the blankets (perhaps
the blankets have a slight insulating value, and at a guess they're
better at retarding evaporation); the ad claims 60% of a blanket's
efficiency. On the other hand, a blanket plus reel for my size pool
(22x44) costs a minimum of $700 and are warranted for 6-8 years, while
the "pills" cost maybe $30 for a four-pack and last "up to" 30 days
(I'd need two at a time for my size pool). So figure four to six per
season (a month or so at beginning and end of season). And the
blanket looks like a lot of hassle to put on and take off, and to
store when it gets hot out, and in the winter.
Presumably the chemical from pill doesn't feel oily when you're
Thoughts? Given the difference, I'm leaning towards the pill, but I'm
skeptical about how well they work. And it's hard for me to do a
scientific comparison, since I only have one pool :-).
On 15 Apr 2007 20:07:00 -0700, " email@example.com"
Ah, faith. Isn't it wornderful.
It sounds like were talkin about 60 dollars for the first and third
year for pills, and 30 dollars every second year.
So if it would help learn which is better, you've got little to lose
by starting out with thepills. Unless somehow they are worthless.
But it's still only 60 or 90 dollars for the first one or two year.s
Even if you have to buy the blanket, you'll be buying it later and it
will last to a later date.
I hadn't thought about it but I guess evaporation does cool of the
water in the pool. Just like one gets cold when he gets out of the
bath, but after all the water on him evaporates, he starts to warm up
again. Even without a robe.
Remember, don't take these pills on an empty stomach.
YA, you just roll them up, and roll them back out. OR you can use the leaf
blower to blow the loose stuff off before or during the roll up process. If
the cover weren't there, those items you mentioned would be in the pool.
"mm" < firstname.lastname@example.org> wrote in message
On Mon, 16 Apr 2007 22:36:50 -0500, Richard J Kinch
Does this mean that one woudln't have to put on skin oil after
swimming. I'm not talking about sunburn protection, just oil that
some peopel use. Otherwise, might not be so good, depedning on how
much there is.
NREL says 1550 Btu/ft^2 of sun falls on the ground on an average 53.4 F
April day in Baltimore. The average humidity ratio w = 0.0052, with
V = 10.4 mph average windspeed, which makes the airfilm conductance
about 2+V/2 = 7.2 Btu/h-F-ft^2.
ASHRAE says an uncovered A ft^2 pool loses about 100A(Pw-Pa), where Pw
and Pa are pool and air vapor pressures. Pw = e^(17.863-9621/(460+Tp))
"Hg (100% RH at Tp (F)), approximately, and Pa = 29.921/(1+0.62198/w).
Maybe R1 with 80% solar transmission, for a clear vs blue blanket.
You might weigh a pill and chop it up or dilute it several times,
homeopathic-like, to treat water in one dark plastic bucket (does
the coverage formula include depth?), and put a pool cover sample
over another bucket of the same kind...
If the pill completely eliminates evaporation and you wrap both buckets
with a few layers of bubble wrap with black plastic on the outside, the
covered one might gain 1240 Btu/ft^2 = 24h(Tc-53.4)1ft^2/R1, which makes
Tc = 105 F :-) The pill version might have 1550 = 24h(Tp-53.4)1ft^2x7.2,
which makes Tp = 62 F.
These will both work better if you paint your pool black
or let it get muddy, like a natural lake in the sun.
It might be about 59 without the pill...
20 W=.0052'humidity ratio
30 PA).921/(1+.62198/W)'ambient vapor pressure ("Hg)
40 FOR TPX.78 TO 58.8 STEP .01'pool temp (F)
50 PW=EXP(17.863-9621/(TP+460))'pool vapor pressure
60 GAIN50-24*(100*(PW-PA)+(TP-53.4)*7.2)'net gain (Btu/day)
70 PRINT TP,GAIN
I really can't imagine how any chemical treatment would cause a solar gain.
My vote is for the solar cover. They work great. They prevent evaporation,
insulate to a small degree, and the very design of them causes solar gain.
" email@example.com" < firstname.lastname@example.org> wrote in message
I also live in Marytland...and last week or the week before when I
peaked under my cover the water was already GREEN... darn..
However I have no experience with these Pills...but years ago I did
try using a blanket in the spring and again in the fall .. honestly it
was moor problems then it was worth becuase the kids were in and out
of the pool every 15 minutes.. their mother (I was at work) got sick
and tired of working the real then covering up the pool..
Never put it back on the pool...figured if the kids would figure out
for themselves whent he water was not tooooo cold...
i don't know about the pills... but i have a blanket and it's worth every
to me.. the reduced evaporation and increase in temps make it worth the
i have a solar heating array as well and the combination extends my swimming
season by at least 3 months
I have a 27,000 gallon pool and I am using solar pills in addition to
heating with 24x12 feet of solar panels (about 40% of the area of the
pool surface, less than the 50% or more recommended) and without the I
feel that the solar panels heat about 8-10 degrees more than pools
around here without a heater, and with the pill it's another 3-5
degrees according to my very unscientific tests. I hope to do some
real accurate tests, as each day is a little different and I could
have been using the pill on a hotter day. Hmmmm, time for two buckets
of water, one with a cc of drops from the pill and one without. But I
can say that the pill is inexpensive ($10 or so retail at beginning of
season) and very convenient, no blank to mess with. I would strongly
recommend the solar heaters though. Check out my web site that I'm
creating (http://www.mypoolkit.com ) for pictures of the solar panels,
they are well worth the money at about $1000 invested. If I have the
heat going to my spill-over spa only, it heats up to 105 degrees in no
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