Neighbor's above ground pool collapsed inward while they filled it with
Just curious if anyone has heard of the experience before. I did not
participate in the pool construction, but I did help with one, years ago.
I recall gravel on exterior of circle, but I still can't figure out from
physics perspective how the pool would concave unless there was some stress
bearing part of side-wall/top which was not secured. I do recall when doing
the liner that there were instructions about how the edge of the bottom of
the liner needed to be a certain way. I am thinking the liner edge on bottom
of pool was mis-alinged and some how applied pressure to the side, above the
bottom of the pool. A theory.
EZ-Set pools seem nice, with the air doughnut at the top... 12'x36"
for $98, 14'x39" for $159, 16'x42" for $218, 18'x48" for $297, at
Wal Mart, including a ladder and pump and filter.
They might last a long time, away from people and out of the sun.
We might put a 12'x3' pool inside a 16'x16'x8'tall greenhouse with 5 $7
doubled 1x3 bows on 4' centers and stretch 2 $20 16'x25' poly film layers
over a $20 layer of 80% shadecloth over the bows and trickle water between
them with Grainger's $157 4RD12 pump, collecting 0.8(620+1000)8'x16'
= 165.9K Btu and losing about 6h(130-34)201ft^2/R1 = 115.8K Btu on
an average January day in Phila, for a net gain of 50.1K Btu/day.
If it supplies 50K Btu/day over 5 cloudy days and 250K = (130-110)P,
it needs P = 12.5K pounds of water, 12.5K/62.3/pi/6^2x12 = 21" deep.
We might float a 10'x1" foamboard disk on top that supports a 300'x1"
$60 HDPE pipe in a flat spiral to heat water for showers, and surround
it all with 2' of mulch or bags of dry leaves.
And cover the pool surface with a 9'x2" foamboard disk supporting a $60
300'x1" flat pipe spiral, with a 12'x12'x2" layer of foamboard over that,
and mulch around the pool up to the foamboard, with whitewash over (how
much of?) the north wall of the greenhouse. The 2x2'(12'+16') = 112 ft^2
of mulch surronding the horizontal collector would act as a parasitic air
heater, warming the air around the collector and reducing its loss.
The pool comes with a filter and a 540 gph pump. With no filter,
it might push water up a few inches above the water level. With
130 F water, it might need a cooling air supply, eg a small hole
in the greenhouse near the ground and another near the peak.
....and black fiberglass window screen over that, and poly film over that.
A separate fountain pump might move a little water over the top of the film
to prevent overheating in summertime. Outdoor air with w = 0.0133 in July
in Phila makes Pa = 0.626 "Hg. At 130 F and 100% RH, Pw = 4.74 "Hg, so
a wet square foot might lose 100(Pw-Pa) = 411 Btu/h by evaporation,
more than the peak solar gain.
....about 4 feet above the collector, to reflect more winter sun onto it.
30 WC'N-S collector width (feet)
40 LC'E-W collector length (feet)
50 HC=3'collector height (feet)
60 AC=WC*LC'collector area (ft^2)
70 RCC=1'collector cover US R-value
80 RC=RCC/AC'collector-greenhouse thermal resistance (F-h/Btu)
90 WG'greenhouse width (feet)
100 LG'greenhouse length (feet)
110 HG=8'greenhouse height (feet)
120 FOR HR=6.9 TO 7.1 STEP .1'reflector height above ground (feet)
130 WUC=WC/2+SQR(HG^2-HR^2)'unshaded collector width (feet)
140 AGC=PI*16*16/2+PI*8^2'greenhouse cover area (ft^2)
150 RVG=.8'greenhouse US R-value
160 RG=RVG/AGC'greenhouse-outdoor thermal resistance (F-h/Btu)
170 GHGAIN=.9*(WG*620+HR*1000)*LG/6'Jan gh gain (Btu/h)
180 CGAIN=.9*(WUC*620+.9*(HR-HC)*1000)*LC/6'Jan collector gain (Btu/h)
190 SACGAIN=GHGAIN-CGAIN'sacrificial heater gain (Btu/h)
200 TA4'outdoor temp (F)
210 TP0'pond water temp (F)
220 TGAT=TA+SACGAIN*RG'Thevenin gh air temp (F)
230 CLOSS=(TP-TGAT)/(RC+RG)'collector loss (Btu/h)
240 CNET=6*(CGAIN-CLOSS)'net collector gain (Btu/day)
250 PRINT HR,"Jan (Btu/day):"TAB(35);CNET
6.9' Jan (Btu/day): 57521.07
7.0' Jan (Btu/day): 57581.57
7.1' Jan (Btu/day): 57579.94
With Pi(7^2-5.25^2)3/27 = 7.5 cubic yards of mulch or bags of leaves inside
a 14'x3' welded-wire fence circle (which would provide some pool reinforcing),
16.4K pounds of 120 F water might lose 5dx24h(120-34)(100ft^2/R24+64ft^2/R20)
= 75.8K Btu and provide (16.4K(130-110)-75.8K)/5 = 50.4K Btu/day of hot water
for 5 cloudy days in January.
I just never heard of this defect. Good advice, but you should see all of
the above grounds which go up in the 'burbs. The air inflated ones appear
to be popular these days, too.
I don't think most middle class wage earners can afford a below ground pool
and the option for above ground looks normal friendly to the pay check. I am
Yes, what probably happened was the liner shrunk from being exposed to the
sun for too long while empty.
Then when you filled it, it ... did what you said.
I made that mistake once. Never drain it fully, try to never drain it at
all if possible.
Also saw it happen to my neighbor... Must be a common problem.
Thanks. That makes sense.
I will need to find out if they waited untill next day, or did not follow
guidelines to be sure liner is sitting on edge of bottom as water fills in.
I recall that initially you need to be in pool making sure liner is tucked
in as water level builds up and applies pressure.
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