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Thread: Hot tub to heat pool?

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    Hot tub to heat pool?

    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. 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
    13 x 24' x52" ultra frame pool (still in the box)
    Going to be set in 2.5' hole with deck at rail height sourounding entirely
    Cartridge filter ( we will see how that goes for one season)
    Natural gas heater and solar cover
    Plan to use bbb method! Yay!!

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    Re: Hot tub to heat pool?

    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.

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    JasonLion's Avatar
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    Re: Hot tub to heat pool?

    Also, most hot tub heaters are electrical resistance heaters. That is by far the most expensive way to heat a pool.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    Re: Hot tub to heat pool?

    But the thing is we already have a hottub and it has maxed out our electrical panel. We cannot add another 220 to put in electric pool heater and the quote we got from gas fitter is 2-3000!!! To plumb natural gas from main to hook up a natural gas heater.
    13 x 24' x52" ultra frame pool (still in the box)
    Going to be set in 2.5' hole with deck at rail height sourounding entirely
    Cartridge filter ( we will see how that goes for one season)
    Natural gas heater and solar cover
    Plan to use bbb method! Yay!!

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    Re: Hot tub to heat pool?

    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?

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    Re: Hot tub to heat pool?

    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
    13 x 24' x52" ultra frame pool (still in the box)
    Going to be set in 2.5' hole with deck at rail height sourounding entirely
    Cartridge filter ( we will see how that goes for one season)
    Natural gas heater and solar cover
    Plan to use bbb method! Yay!!

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    Mod Squad jblizzle's Avatar
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    Re: Hot tub to heat pool?

    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.
    Jason, TFP Moderator
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    Re: Hot tub to heat pool?

    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.

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    Re: Hot tub to heat pool?

    I won't keep it up last sept 15th. But I would like it to be warm enough to enjoy and our back yard doesn't get sun for more that a few hours per day maybe we will have to put a rush on the heater.... Why is using house hot water tank not a good idea??
    13 x 24' x52" ultra frame pool (still in the box)
    Going to be set in 2.5' hole with deck at rail height sourounding entirely
    Cartridge filter ( we will see how that goes for one season)
    Natural gas heater and solar cover
    Plan to use bbb method! Yay!!

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    Mod Squad jblizzle's Avatar
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    Re: Hot tub to heat pool?

    Quote Originally Posted by kshuf
    Why is using house hot water tank not a good idea??
    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.
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
    500 sqft Heliocol solar panels, ThePoolCleaner, TF-100 test kit w/ SpeedStir
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    Re: Hot tub to heat pool?

    But could I use hot tub water and also fill from hose inside the house on kitchen sink, draining the hot water? Would that make a difference you think? 3-4 fills of the hottub and 3-4 fills till hot water runs out in house? Would that help?? Then keep cover on to keep warm
    13 x 24' x52" ultra frame pool (still in the box)
    Going to be set in 2.5' hole with deck at rail height sourounding entirely
    Cartridge filter ( we will see how that goes for one season)
    Natural gas heater and solar cover
    Plan to use bbb method! Yay!!

  12. Back To Top    #12
    Mod Squad jblizzle's Avatar
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    Re: Hot tub to heat pool?

    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.
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
    500 sqft Heliocol solar panels, ThePoolCleaner, TF-100 test kit w/ SpeedStir
    Pool School + Test Kit + PoolMath = A TROUBLE FREE POOL
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    Re: Hot tub to heat pool?

    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
    13 x 24' x52" ultra frame pool (still in the box)
    Going to be set in 2.5' hole with deck at rail height sourounding entirely
    Cartridge filter ( we will see how that goes for one season)
    Natural gas heater and solar cover
    Plan to use bbb method! Yay!!

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    porkandbeans's Avatar
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    Re: Hot tub to heat pool?

    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.
    5,061 gallon Intex Ultra Frame 16x48 Saltwater Krystal Clear
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    Re: Hot tub to heat pool?

    Interesting theory!!
    13 x 24' x52" ultra frame pool (still in the box)
    Going to be set in 2.5' hole with deck at rail height sourounding entirely
    Cartridge filter ( we will see how that goes for one season)
    Natural gas heater and solar cover
    Plan to use bbb method! Yay!!

  16. Back To Top    #16

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    Re: Hot tub to heat pool?

    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.
    8638 gallon 20'x52" Intex ultra frame round AG. 2650 gph Intex Sand Filter. Intex krystal Klear SWG. (newer model that includes copper ion generation) Hayward 1091LX skimmer, Kreepy Krauly lil shark. Taylor K-2006 w/speed stir and sample sizer. New this year, Intex PureSpa - dichlor-> bleach method for sanitizing.
    New pool, 16'x36' (approx 18000 gal) in ground pool, Haywood DE filter

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    linen's Avatar
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    Re: Hot tub to heat pool?

    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?
    TFP Expert who uses Pool School and my TF100 test kit along with PoolMath for my: Round 11K gallon AGP with deep end, 20" sand filter, Matrix 1hp 2spd, 6 2ftX20ft solar panels (and solar cover!), Intex SWCG (copper bars disconnected) and a Rubadub hot tub (chlorine). The SLAM process is not finished until: 1. CC < 0.5 ppm, 2. An OCLT < 1.0 ppm and, 3. The water is crystal clear.

  18. Back To Top    #18

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    Re: Hot tub to heat pool?

    We will use a solar cover. Pool is not up yet. Waiting now on a guy with a machine to dig to.level
    13 x 24' x52" ultra frame pool (still in the box)
    Going to be set in 2.5' hole with deck at rail height sourounding entirely
    Cartridge filter ( we will see how that goes for one season)
    Natural gas heater and solar cover
    Plan to use bbb method! Yay!!

  19. Back To Top    #19

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    Re: Hot tub to heat pool?

    Quote Originally Posted by PridgNYC
    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?
    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.

    Quote Originally Posted by PridgNYC
    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.
    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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