I built a similar system after seeing yours. I used a CAMPLUX ENJOY OUTDOOR LIFE Pro BD158 1.58GPM Outdoor Propane Tankless Gas Water Heater and a Harbor Freight 12 Volt DC Transfer Pump (Drummond- Item#63324) --290 GPH max. When I started, the hot tub was at 83 degrees. I had the water heater turned to maximum flow and about mid way on the temp. It put out 45-46 degree C water (about 114 degress F.) In 30 minutes, the hot tub was at 90 degrees F. I like it. :)
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Very nice. I have a similar Intex hot tub and I love it. The stock heater is puny, so I have considered doing something similar to you instructible. Tell me more about how much propane your system uses.
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Thanks! It kept me warm last night, once again.
We gotta keep that wind from freezing us. :)
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