Hot tub to heat pool?

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K

kshuf

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Jun 11, 2013
79
Southeastern British Columbia
I saw a video on YouTube where a guy used two sump pumps to circulate water between pool and hot tub to heat up his intex type pool. :shock: Any here ever had any success with this method? We are looking at a natural gas heater possibly but it gonna cost a small fortune to run the natural gas from the main to the heater... Arg

We have a hottub sitting about 2feet from where the pool will be installed. We are doing a deck around both... And putting up an intex pool 13 x 22 ft
 
It still takes the same amount of energy to heat the hot tub water as it would to heat the pool water, so you wont save any money. The hot tub heaters are probably not powerful enough to heat the pool very well.
 
Do hot tubs and pools have the same water chemistry requirements? I don't know, so I'm just throwing that out there, but I suppose the pool could be responsible for maintaining the hot tub's water.

I think the OPs intent is to save on installation cost, not save on heating costs. I would recommend a float valve to keep the hot tub from either over flowing or from being drained down. Have you compared the heat output of a pool heater to a hot tub heater?

Also: you can not add 'another' 220 connection. Could get an electric pool heater, and then unplug the pool heater when you heat the hot tub and vice versa?
 
Thank you so much for the input. We have decided to go ahead with adding natural gas. My brother in law is a gas fitter but he lives about 7 hrs drive away. He is gonna come and do it for us anyways. But prob not till next spring so we shall use the heated hot tub water for this year. We will just heat the hot with garden tap water and pump straight into the pool, repeat 2-3 times over 1-2 days then top off pool water with cold water from the garden tap as well. Then we can cover with solar cover and hope for heat retention. It will be short swimming season but its ok! At least we will have a heater next year :)
 
What is your goal? If you just want the water a little warmer, then for only a few $100 you could add a few large solar panels. Coupled with the use of a cover at night, you should see a good jump in temp during the summer. But if you are trying to maintain the water significantly warmer than the air temps (like in the winter), then clearly you will need a gas heater.
 
I think that what you are trying to do will not work. Any heat gain that you get from a few dumps of hot water from the hot tub wont last long. If you add two hundred gallons of 104 degree water from your hot tub to your 10000 gallon pool it wont make a noticeable difference. You would be better off using your homes hot water heater to heat the pool. Also not a good idea.
 
kshuf said:
Why is using house hot water tank not a good idea??
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Because they are not designed to heat up that much water. They are designed to heat a tank of around 40 gallons of water at temperature with low flow rate. Pool heaters are designed to heat a higher flow rate of water just a few degrees which is more efficient.
 

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It will "help", but not sure how noticeable the temperature change will be.

Try it and report back the results ... we are simply saying that you are likely expecting too much.
Say you have 10,000 gallon pool at 70 degrees. Adding 40 gallons of 120 degree water from the house and 200 gallons of 104 degree water from the spa will raise the pool from 70 to ~70.8 degrees ... ignoring any loses to the environment.
 
Yeah that isn't much :( it's going to be approx 8000 gallons pool might under fill it for this year as low as the outlet will allow ... Really wish we could get heater up and running but local company quoted 2-3000$ to do gas fitting where as brother in law will do for a case of beer :) love Canadian bartering!! Lol. But as his wife is due with 2nd child in a months time he can't really make the 6-8 hr trip anytime soon just to hook is up. Then after babe is born they won't want to be traveling for a bit either. By the time they danger here swim season will be done .... Sigh
 
I may not have the best solution for the OP, but I'm interested in this topic.
Allow me to toot the horn of Softub a bit. When I was hot tub shopping and researching, I decided on Softub for power efficiency. Most hot tubs use gas or 220v electricity and are power hungry to use. Softub is quite different whereas it heats without the use of a "heater". As the 110v filter pump cycles the water, the heat from the blower motor is used to warm the water. You set the thermostat at your desired temp and the filter pump turns on as often as needed to maintain the set temp. It takes much longer to heat than a convention tub, but the energy cost is much lower. For instance, after filling with fresh water, it takes me 24 hrs to reach temp. (I set mine at 100*F.) Then it always stays hot by turning on a couple times per day. The reason I am explaining this is to show efficiency. In fact, it is so efficient that my tub has remained at 100*F for the last 1.5 years without anybody using it. (Not something I am proud of.) I don't notice any difference in my power bill.
So I'm thinking, if you hook up a Softub motor pack, you can cycle the water and add heat at will. Maybe put it on a timer a run 6 hours a day and aim for 82*F? You can probably find a used motor pack online for $100-$200.
Just a crazy thought but it might be worth some consideration.
 
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Not really a theory, recycling heat is an old idea. You need to run a filter, and it generates heat in operation, why not use that heat to heat the water? It is actually cheaper (energy wise) under most circumstances to maintain a certain temperature than to raise or lower temperatures to an extreme degree in a reasonable time frame.
 
I don't think a softtub pump/heat system will make a dent in the pool temp. The softtub is small and well insulated, the pool is big and not well insulated.

@kshuf...are you using a solar cover at night?
 
PridgNYC said:
Not really a theory, recycling heat is an old idea. You need to run a filter, and it generates heat in operation, why not use that heat to heat the water?
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All pumps heat the water. When you run your pump of the electricity will end up heating the water - because of conservation of energy, the pump will add energy to the water to cause it to move, and all that energy will become heat.

Electric motors are typically better than 80% efficient, so if you spend $10 running your pump then you have added $8 worth of electric heat to your water. Softub will add $10 worth of electric heat.

PridgNYC said:
It is actually cheaper (energy wise) under most circumstances to maintain a certain temperature than to raise or lower temperatures to an extreme degree in a reasonable time frame.
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The opposite is true. The pool will reject heat to the environment as long as it is heated. If the pool is heated for shorter durations, then it will loose less heat and thus less heat has to be added.

For example, say a family only uses the pool on the weekend. If the heater is turned on Friday morning and turned off Sunday evening, then the pool will only be loosing heat for three days. If the pool is heated all week then the pool is loosing heat every day. And since the pool needs to be the same temperature each weekend, more heat loss equals more heat that has to be added. Heating up the pool on Friday might cause the heater to run for 24 continuous hours, but leaving the heater on all week (four extra days) might cause it to cycle on for a total of 40 hours in those 4 days. You may be tricked into thinking you are saving money by leaving the heater on all week because the heater only cycles on for a couple of hours at a time.
 
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