The pool I just bought (on sale for less than price shown here) is an Intex 18' x 48", which holds 5400 gallons.
After a lot of research and reading loads of reviews and then trying it all out, I feel the perfect combination is this:
Intex 18 foot x 48" round, which has the better (more GPH) pump than the 15' round, includes cover, and ladder, and maintenance kit. I also bought the separate option of the salt water chlorine generator. Also bought the Solar Pro AquaQuik 4512 solar pool heater, and a $50 15' solar pool cover (bubble wrap type). Note the 48" is the height of the inflated ring, and the pool water height is less than 38 to 40".
This is July but when I filled the pool with cold city supplied water (our house is served by Lake Michigan)and we are in Chicago metro area, the initial temp was 66 F. We had some cloudy days initially, and ironically not as warm weather as we are used to seeing at this time of year. With the pool in the shade for most of the morning until noon, it doesn't get sun until after that. The temperature of the pool, went from 66 to around 70F on its own without the 4512 heater, and without real hot days. Now that I have the heater on today, its gone up about 4 degrees. I also just added this afternoon the 15' solar pool bubble wrap cover. That should hold the heat effectively, and in combination of the sun getting through the clear plastic, and this little gem of a radiator, I'm guessing the pool will get to 80F in one or two more days of this 85 to 87 weather. Not too shabby.
The reason to buy the 15' round solar cover, is that it floats and fits perfectly INSIDE of the inflated ring. You put this on in afternoon or whenever kids aren't swimming and it helps to keep it warmer, and then at night, you can simply use the pool cover that fits over the 18 foot inflatable ring, right over the solar cover. Both in tandem should work just fine.
The hoses that came with the pool pump for the Intex 18 foot pool work good with the 4512 heater, and if you bought the Intex salt water chlorine generator, there is one extra hose with that, and the right adapters (these do come with the pool and the heater), and along with one extra medium size hose this Solar heater provides, its a perfect and very easy to assemble combination. With this heater at at around $115 price, the Intex pool, and salt water generator, and lastly a $50 solar cover, I'm all in at less than $500. No chemicals, no expensive gas fired heater, about (4) $5.00 bags of Morton 40 lb bags of pool salt 9can be found at Walmart), 5000 gallons of water, and wa la you have a pretty decent set up that works for kids up to early teens, and very nice for adults who get "hot" mowing the grass, and taking care of the kids all day, and their "needs" so you can take a well earned cool dip in the evening when the kids are all worn out and calmly playing their xboxes or Wii's.
My only suggestion, and its a minor one for the solar heater mfg., is to simply supply two 10 foot hoses, instead of the ~2 foot and ~4 foot ones that require the panel to be so close to the pool pump set up.
Other than that, folks, how can you go wrong ?
The pool can be taken down during the winter, and re-set up each year in about an hour, and versus an inground that may well be nicer, this is at least a factor of 80 to 100 times less expensive. And its not permanent either, so if you get tired of dealing with pools each year, then you just roll out some new sod in the 18 foot circle you burnt out in your yard !
The solar salt water generator is a very cool device. It works with copper ion genrator, which converts the salt water to a very low level of chlorine. Barely detectable chlorine smell, crystal clear water, and the copper ions kill all the bacteria, along with the small amount of chlorine. Its very soft water, and like swimming in "Visine." Follow the directions, and definitely use the granular pool salt, pour it in around the edge of the pool a bag at a time, then stir it up using the pool brush and handle that comes with the pool. It will dissolve quickly, but I suggest running it with the pool pump for the full 24 hours so its thoroughly mixed. The chlorine generator will work better that way, and note that I tried to do it sooner,and it wasn't until all the salt was in there, and it had been mixed for a day that all the chemical strips tested out properly, and the pool had a good "balance." It will take the recommended full 135 lbs of salt to get PPM up to the right level of salt. The directions are all pretty decent, but some of these high level tips may help you avoid some anxiety or trying to short cut anything, as we men often like to do. (women are better at following directions so for the moms who read this, just ignore what Im saying to the "men.")
P.S. The kids ranging from 8yrs to 15yrs absolutely love the pool. They'll probably get "bored" of it in a few weeks and then its back to school. $500 for this gig is less than a family of 5 would spend for one JUST ONE weekend of so called "fun" at a place like six flags, or some other commercially oriented place that is there to take your hard earned money. If I only get 2 or 3 seasons out of this, it will have been more than worth the modest investment. In just a couple of days of use, I already feel pretty good about the purchase even if something tears or breaks. Parts are easy to find too, and again, think about the fact a new inground pool maybe twice this size will run you at least between $40k and $50K without landscaping, take tons of chemicals that run you about $400 per year, and gas bills for heating it close to an extra $200 per month when you do need the heater.
P.P.S. It takes about 15 to 16 hours to fill this pool with water from the garden hose. I didn't see that mentioned in any review of the pool, and so I thought I'd give the tip in case you are looking to buy this combination. Unless your yard is fairly level, and not on any slope, expect to buy play sand to level it. Also, If you are thinking of the 15' round pool, I'd humbly suggest you spend the extra few tiny $, and go with the 18' since it has the larger 1-1/2" hoses, more powerful pump, pool maintenance kit, and is about 15' round on the inside of the inflated ring at the top. (hence the purchase of ONLY a 15 ' solar bubble wrap cover. which fits neatly inside of the ring, and ring sort of protects it from easily blowing off the pool. if it gets windy, then just add the Intex cover which wraps over and around the inflated ring, and has a slick tie rope to hold it in place.) And even if you aren't willing to wait until mid-season when these typically go on sale, its still worth the $300 to $400 price you likely would pay for just this pool, plus any extra's for the heater, and salt water generator, and solar cover combo. Good luck and enjoy the fun !