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Thread: Using pool heater to keep large water tank warm

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    Using pool heater to keep large water tank warm

    I hope this isn't against the rules, as its only semi pool related.

    I have a lawn care company, and I am trying to heat a 2000gal water tank to around 80-90 F. This tank is kept inside, and water is drawn from it in 50gal-250gal at a time. The tank is filled by a 3/4 water line, with an automatic shut off when water level reaches the top.

    My plan is to install an in line water heater on the tank fill, then use a recirculating pool heater pump to maintain the temperature. Heater would ideally be electric, as the tank is indoors. I'm hoping the whole system can be a "set it and forget it" type system that either turns the pump and heater on by a thermostat, or the pump runs indefinitely and the heater turns on by thermostat. The outside of the tank can be insulated to minimize heat loss, so I suspect I can get away with a smaller size heater. Is this possible with normal pool\spa equipment?

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    Re: Using pool heater to keep large water tank warm

    Hmmm, sounds like your doing an indoor hot tub I have a 6kw for my tub at 700 gallons, it may be enough if yours is insulated... if not I would get the 11kw...

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    Re: Using pool heater to keep large water tank warm

    I agree that a hot tub control system will work great for what you are looking for. You can set the temp and it will come on every hour or so and heat as required. I would get the smallest heater and pump available since you won't be losing heat as you would in a hot tub with the lid open and air jets on and you aren't looking for a quick recovery or ability to maintain 100+ degree temp in those conditions. I would think even the smallest 3-4kWh heater will be able to maintain 90 pretty easily.

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    Re: Using pool heater to keep large water tank warm

    I agree sounds a lot like an indoor hot tub, as to what you will need, I suspect you may be best off with a pair of 6KW hot tub heaters and a pair of circulation pumps, with controllers so you have some redundant safety as their are potential failure points (pump, heater element, high and low thermocouples, control board, and of course simply tripping a ground fault or breaker). There are some factors you don't mention like how often do you need to remove water, as I suspect a single 6KW heater would have no problem maintaining a 2,000 gallon semi-insulated tank at 80 degrees, but could have issues warming the water if you were to pull 250 gallons out of it multiple times per day and have near freezing refill water.

    There may be some other factors to consider depending your usage, assuming you are on a municipal water supply I suspect you would be required to install a backflow prevention device if you don't have one which will likely cost a few hundred dollars. Also depending on your usage you may need to consider some water sanitation option if you plan to hold your water for a long time.
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    Re: Using pool heater to keep large water tank warm

    A in-line water heater will be installed on the tank fill. I'd say on average ~1500 gallons are removed during peak use. Water is pulled from municipal water. Multiple back flows are installed.

    If I were to buy this control unit/heater http://www.hottubwarehouse.com/balbo...mplete-54216-z and this pump http://www.hottubwarehouse.com/water...ump-3410020-1e I should have everything I need?

    Are these pumps intended for 24/7 circulation or does the controller switch it on and off at timed intervals? Is the pump wired directly to the controller or is there a relay inbetween?

    Thanks for the help its much appreciated

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    Re: Using pool heater to keep large water tank warm

    I have the same 1/8 hp pump in my spa that runs 24/7 and has been for over 4 years now I am not sure how it connects to that board but I am sure it will have it in the instructions..

    the instructions may be here Balboa Water Group - Manual Instruction Sheets

    having the heater on the tank fill is the wrong way to install this... you will have to plumb in a recirculation system to constantly curculate the water through the heater 24/7, that is where the pump comes in... you would use a simple 1 in and 1 out system, probably use 1.5 inch flexpipe... I do not think you will need a filter but with heated water you may have to look at some kind of chlorine system to keep algae at bay...

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    Re: Using pool heater to keep large water tank warm

    If you are considering an inline water heater, why not just install an LPG, on-demand water heater on the outlet side and be done with it. The operational cost would have to be lower......

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    Re: Using pool heater to keep large water tank warm

    That would probably work better if the gas supply was there... they also make electrical units but you would have to ensure it could keep up with flow...
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    Re: Using pool heater to keep large water tank warm

    Quote Originally Posted by cowboycasey View Post
    That would probably work better if the gas supply was there... they also make electrical units but you would have to ensure it could keep up with flow...
    i have been told that electric on-demand water heaters can be installed serially (one after another) for greater heating if needed.

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    Re: Using pool heater to keep large water tank warm

    I am not sure exactly what your goal is here, or how much you care about operating cost, but any electrical resistive heater is going to cost a lot of money to run, which has me thinking maybe a more out of the box option would be best. I suspect all pool heat pumps would be overkill, but they do get about 3-4 times better efficiency than resistive heat, however they loose that as the temperature difference increases (outside temperature gets colder), and and likely fail to heat at all when it gets below about 20F outside. Another alternative to explore would be solar heat from a glazed solar heater panel, again your goal temperature is much lower than domestic water heating, so there is real possibility here without it being way too large, but then you get the issue of no hot water when the sky is cloudy.
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    Re: Using pool heater to keep large water tank warm

    Quote Originally Posted by Isaac-1 View Post
    I am not sure exactly what your goal is here
    The problem we are having is we can't dissolve enough of the type of fertilizer we want to use in water at its current temperature.

    The goal is to have hot water on-demand, all the time. The outlet pump pulls nearly 100gal/min so having an in-line water heater there isn't really possible. The purpose of the in-line heater on the tank fill is so I can still have hot water available after 1500gal has been removed, and the tank continues to fill itself. The spa heater will maintain the temperature when not in use.

    I'm not too worried about the energy bill, I won't need to keep the tank heated all year and it's just the cost of doing business. Next year I may install solar heating panels to lower the energy bill, but I'm looking for a solution ASAP.

    As far as LPG goes, it would require more work to install and I don't know the fire code involved with having an LPG appliance in the same vicinity as fertilizer is stored. But I suspect the fire department won't like it.

    I don't think algae build up will be an issue when the contents of the tank are exposed to no light. My water doesn't have a signficant amount of phosphates in it either.This water is mixed with beneficial soil micro-organisms and chlorine would degrade the microbes pretty quickly.

    I have an electrician coming Tuesday to run the 220v for me. I'm going to go with the balboa control pack and recirculating pump with an in-line heater. If for any reason I shouldn't do this, please speak now


    Thanks for all your help guys.

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    Re: Using pool heater to keep large water tank warm

    Sounds like you have a plan, I think the Balboa control pack along with a recirculating pump and a 5 or 6KW heater will likely do what you are after. From what you say I assume this use is seasonal and not year round, and also that it is not so critical that 24-48 hours of down time should a part fail would be critical to your operation. I can't comment too much on the specific components you have listed, other than to say I suspect that circulation pump is much larger than you need, and Balboa controls are in most of the brands of hot tubs that don't use their own in house controllers. Some specific models have better reputations with the repair people than others, but I don't know enough about them to say more than that. On the topic of circulation pumps, I have a Hot Spring brand tub, Hot Spring / Watkins has their own in house designs for heaters, controllers and pumps (or at least they don't use common commodity ones). The current Watkins circulation pump used on all their tubs with heaters from 1.5 - 6KW or so is the E5 pump with 3/4 inch fittings Circ Pump, E5 (Silentflo 5000 & 5002 Factory Replacement), 74427 it comes in 1 and 2 speed varieties and also 120 or 240V, basic model is rated at 6,000 gallons per day.
    Indoor 20x40 35,000 gallon vinyl pool with 1.5 HP 2 speed Jandy FloPro pump, Hayward EC75 Perflex DE filter, 11 4x12 Techno-Solis solar panels w/ Aquasolar controller, Aquabot Turbo T Robot Cleaner. Also LMI metering chlorine dispenser pump and HotSpring Jetsetter
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    Re: Using pool heater to keep large water tank warm

    Quote Originally Posted by spazzedface View Post
    The problem we are having is we can't dissolve enough of the type of fertilizer we want to use in water at its current temperature.

    The goal is to have hot water on-demand, all the time. The outlet pump pulls nearly 100gal/min so having an in-line water heater there isn't really possible. The purpose of the in-line heater on the tank fill is so I can still have hot water available after 1500gal has been removed, and the tank continues to fill itself. The spa heater will maintain the temperature when not in use.

    I'm not too worried about the energy bill, I won't need to keep the tank heated all year and it's just the cost of doing business. Next year I may install solar heating panels to lower the energy bill, but I'm looking for a solution ASAP.

    As far as LPG goes, it would require more work to install and I don't know the fire code involved with having an LPG appliance in the same vicinity as fertilizer is stored. But I suspect the fire department won't like it.

    I don't think algae build up will be an issue when the contents of the tank are exposed to no light. My water doesn't have a signficant amount of phosphates in it either.This water is mixed with beneficial soil micro-organisms and chlorine would degrade the microbes pretty quickly.

    I have an electrician coming Tuesday to run the 220v for me. I'm going to go with the balboa control pack and recirculating pump with an in-line heater. If for any reason I shouldn't do this, please speak now


    Thanks for all your help guys.
    the bold part is where I have the question... how long before emptying the 1500 gal, filling and emptying again?

    if this is done once a day you should be good with a 5 to 6kw heater.. if this is done 2 or 3 times a day and you need hot water for each time you will need an 11kw heater to heat faster... it will also depend on water temp for fill

    I found this to give you an idea of what I am talking about

    Lets say you have a 350gal tub.
    @120v the 1.5kw heater draws 12.5amps
    @240v the 4kw heater draws 16.667amps
    @240v the 6kw heater draws 25 amps

    1gal water=8.33lbs*350= 2916.666lbs
    1BTU=watts*3.41214
    BTU/lbs= change in degrees/hour

    1500*3.41214= 5118.21/2916.666= 1.75degrees/hr
    4000*3.41214= 13648.56/2916.666= 4.68degrees/hr
    6000*3.41214= 20472.84/2916.666=7.02degrees/hr

    a 1.5kw@ 120v will heat the tub @ 1.75 degrees/hr
    a 4kw@240v will heat the tub @ 4.68degrees/hr
    a 6kw@240v will heat the tub @ 7.02degrees/hr

    They used a 350 Gal insulated hot tub as an example..

    here is 1500 gal example

    1gal water=8.33lbs*1500= 12495lbs
    6000*3.41214= 20472.84/12495=1.63 degrees/hr

    so with a 6kw heater and fill water of X degrees you would have the following in 24 hours
    fill / 24 hours
    50 / 74
    60 / 84
    70 / 94

    11kw heater
    1gal water=8.33lbs*1500= 12495lbs
    11000*3.41214= 37533.54/12495=3 degrees/hr

    so with a 11kw heater and fill water of X degrees you would have the following in 7 hours
    fill / 7 hours
    50 / 71
    60 / 81
    70 / 91

    these are approxamate as it will depend on how insulated the tank is, outside temp, fill water temp and TIME....
    Pool: Intex 16x32 15000 gal, 2 speed 340042, Pentair CC320 Filter, CircuPool SJ45 Salt System, Intermatic PE653RC; Hot Tub: 650 Gal SWG Megachlor
    links: pool school * Recommended-Levels * SLAM * CYA chart * Test kits * How To Post Pictures * Poolmath * OCLT ** Support your website if we helped you :) **

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