DIY EMT Solar pool heater

*I haven't double checked these numbers, but it seems to be close - my math could be off...

Typical solar insolation is around 7 kwh/sq meter in your area in the summer. Or 7k Joules per second.
Water requries 4.2k Joules per kilogram per degree C.
550 gallons is 2082 kilograms. From 66F to 80F is 16F difference or 9 degrees C.
This nets a requirement of 78,699.6k joules to heat the 550 gallon pool. Assuming a solar insolation of 7kwh/sq meter, then a 1 sq meter heater at 100% efficiency would take 11,242.8 seconds to heat the pool - or approximately 31.23 hours. Obviously this won't work because you only have ~12hrs worth of insolation, and likely a lot less 'effective' hours depending on shade/angle.
So let's assume that the height of insolation will last approximately 4 hrs, then we need 7.8 times more area. So now the solar heater has to be ~8 sq meters. But a solar heater is not 100% efficient, and will need some excess capacity in order to deal with wind, shade, etc. At 71% efficiency (a figure I found on some random solar heater page) that brings us to 11sq meters or approximately 100 sq ft.
With 10ft long conduit you'd need 10' worth of width as well - at 1/2 diameter that's 240 10' lengths of conduit, or 2400' of conduit, or $624 worth of conduit prior to hoses, connections, etc.

Even trying to use all 7 hrs, this would only cut the system to ~50 sq ft and ~$312 worth of conduit.

Now, this assumes the pool will lose all heat at night, every night. Which isn't the case. This also makes a ton of other assumptions which are likely not accurate, but is a good conservative sizing exercise. Based on the roof-mounted pool heaters I used to see in Vegas all the time, this size seems fairly reasonable.

If it were me, I'd buy a few rolls of HDPE piping and try to roof mount. 1" non-potable HDPE is about $55 for 300 ft, or about $220 for 1200ft worth, but there's still the cost of assembly since HDPE doesn't like to make bends. I'd build it with a bunch of T's to make a radiator-like layout, but even at 20' wide that's 120 T's. Or it may be possible to just lay out a flat coil or two, which would reduce the number of fittings. Roof mounting would still be a good idea since it will help cool your roof while heating your pool.