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Stock tank solar + electric hot tub

Bgcal

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Apr 15, 2022
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I’m planning to set up a DIY stock tank solar + electric hot tub and hoping to get some feedback on the setup.
170-gallon 2x2x6’ tub, insulated, out through an inline strainer, then to an intex 1500gph pump/filter. Then it would split into 2 loops, controlled by b-hyve or similar wifi irrigation controllers.
Loop 1 would go to a 4x8’ rooftop solar thermal panel followed by a temp sensor and one-way valve.
Loop 2 would go to an in-line pressure-activated electric heater on GFCI. Loops then join and return to tub.
Solar loop open ~10am-4pm, actuated by pump. Thermostatic safety cutoff of pump if heat exceeds 118 or so. Solar loop closed in evening. Electric loop opened to heat for use – has its own thermostat up to 145C. Hardwired to GFCI.

Parameters:
• Pretty committed to the fun/challenge/cheapness of DIY with off-the-shelf parts. I know it may not prove cheaper in the end.
• Have a small space, so this size tank is perfect for me.
• Idea is that solar would do initial/maintenance heating, electric would be the peaker when using tub.
• Need hot water (104 doesn’t cut it so conventional spa heaters are out).
• Live in northern California, so no freezing or extreme weather issues (only fires and earthquakes!)
• I’m fairly handy but not a technician or tradesman, so simple is preferable to perfect.

Feedback I’d appreciate:
• General ‘will this work?’ assessment
• Fatal flaws, safety issues.
• Tweaks to optimize/improve within those parameters.

Specific Questions:
• What sorts of hoses/lines should I use? I’d prefer to not have to use rigid PVC throughout, especially for the run to the solar panel. Can I use PEX? 1.5"/2” Intex hoses? Will need off-the-shelf joiners/gaskets for tank, pump, controllers.
• How sensitive would the various components be to variations in line diameter? I’d need to step down to a garden hose for the irrigation controllers, plus whatever line goes to the solar. Controllers have a ~700gph flow rate. Will that burn out the pump? Heater requires a bit of pressure to activate too.
• How do you connect a thermostatic probe to a hose? Not at all obvious to a noob like me.
• Can this system power some minimal jets on return to the tub? Not a priority, but another thing that’s hard to glean from casual reading.
 
I’m planning to set up a DIY stock tank solar + electric hot tub and hoping to get some feedback on the setup.
I set up a similar unit to you, but more for cooling to suit our warmer climate. The heating was just to extend the season.

"What sorts of hoses/lines should I use? "....Similar to what is on your pump but better quality. The hose that comes with the pump only lasts a season in the sun and chlorine. How better depends on the price and what is available. The most expensive seems too inflexible. Try and avoid our mistake of having too many joiners as the plans evolved.
The 20mm plex in our diy solar heaters seems to last forever and were Teed in // with the larger pipe so not to restrict the flow.

The pump ran continuously since not in the same scenario as yours. These little pumps defy expectations except no good for the water jets! Only switches were for the blue underwater 12v led lights and the mains air pump. The heating elements were wired directly to the panels.

A redneck swimming pool as they say in Wyoming.....
 
I set up a similar unit to you, but more for cooling to suit our warmer climate. The heating was just to extend the season.

"What sorts of hoses/lines should I use? "....Similar to what is on your pump but better quality. The hose that comes with the pump only lasts a season in the sun and chlorine. How better depends on the price and what is available. The most expensive seems too inflexible. Try and avoid our mistake of having too many joiners as the plans evolved.
The 20mm plex in our diy solar heaters seems to last forever and were Teed in // with the larger pipe so not to restrict the flow.

The pump ran continuously since not in the same scenario as yours. These little pumps defy expectations except no good for the water jets! Only switches were for the blue underwater 12v led lights and the mains air pump. The heating elements were wired directly to the panels.

A redneck swimming pool as they say in Wyoming.....
Pictures and/or parts list/suppliers would be greatly appreciated.
I have a number of PEX & Poly products which I purchased for rain catchment, heating/cooling barrels of water for climate control in the greenhouse, heating/cooling my house, etc.. All of which I bought too much and too many of in the hopes of someday having a "Stock Tank Tub". My bony arse needs a good seat; suggestions are welcome.

I am still assuming we're talking about a stock tank hot tub and not a heated stock tank & a hot tub. I'm going to feel like a real dork if I am wrong.

@Bgcal Chime in anytime, preferably before I dig a really deep hole that fills with hot water. ?
 
Correct- a stock tank hot tub. Key links in The original post.
Actually seems like the 1000gph pump (not the 1500) might be better. It has 1-1/4” hoses, so the other elements wouldn’t be as far off. Figured out I can get to a 1” diameter at the tightest point using a sprinkler solenoid (vs a 3/8” hose). That with 1” PEX seems worth a go.
 
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