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Thread: Heater size questions

  1. Back To Top    #1

    Join Date
    Jul 2015
    Phoenix AZ

    Heater size questions

    Hey everyone! I'm new to the forum and in the process of having our first pool built. We are building a pretty small pool/spa combo that I've learned is commonly called a spool or cocktail pool. A bit smaller than a standard play pool.

    Pool will be about 7500 gallons I think (my calculations could be wrong). 250sqft and 65 foot perimeter. Location is Phoenix Arizona.

    My question is trying to determine gas heater size. Our goal is to be able to heat it up to spa temps in the winter time, we don't want to wait all day for it to heat up. Pool builder is recommending a 250k btu heater, but I'm thinking a 400k btu heater will be better. Pool builder says 250k will heat up to 103 degrees in a few hours...I'm not so sure. Pool builder is also installing heat returns if that makes a difference (I don't know too much about this stuff yet). This will be supplied by a new gas line 2 inches in size.

    I can't seem to find any accurate info online because my pool is sort of in between spa and pool size. Any my thoughts or input would be much appreciated. Anyone here go with a smaller heater and wish they would've went bigger?
    Pool build in progress.
    7500 gallon spool/cocktail pool
    Phoenix AZ

  2. Back To Top    #2
    Mod Squad Patrick_B's Avatar
    Join Date
    Jun 2011

    Re: Heater size questions

    Welcome to TFP!

    I agree with the PB, but if you don't mind spending the cash, and want fast heat, then get the 400. You can have too little heat, but it's difficult to have too much if you want it. I'll say 400 is overkill, but if that's what you want, it's your money.
    TFP Moderator
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  3. Back To Top    #3

    In the Industry

    Join Date
    Jun 2015
    Wildomar, California

    Re: Heater size questions

    I would go with the 400 over the 250, based on what your purpose is as to heating the pool. Gas line size should be correct as to the pipe size and importantly, the gas meter. The real difference is cost of the heater. As far as to the cost of the gas, the 400 uses more gas but since it heats up the pool faster, you loose les heat to the air.

  4. Back To Top    #4

    Join Date
    Jun 2012
    western NY

    Re: Heater size questions

    A 250K heater will change the water temp about 3 deg per/hr. a 400K heater change the water temp about 5 deg/hr
    Unknown make 18' above ground (bought used in 1999) Sparco sand filter. Hayward 100,000 BTu heater. 2 speed pump

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