Hayward 400,000 BTU Natural Gas Pool Heater Review

Hayward 400,000 BTU Natural Gas Pool Heater Review

It can often be quite an investment trying to find an appropriate heater for your swimming pool. Depending on the size of the pool, it can take varying amounts of time and power in order to keep everything conditioned correctly. If you’re willing to spend a bit of money, however, you can get pool heaters that are both fast and efficient. Of course, price isn’t necessarily an indicator of quality, but it does help quite a bit.

In particular the H400FDN from Hayward is a 400,000 BTU natural gas pool heater that can heat most pools within a few hours. It’s a little bit on the pricey side, but it does work as advertised, and when it works it tends to do its job fairly well. For those who don’t mind spending a fair bit of money, it’s a reasonable purchase to make.


One of the most touted features of this pool heater is its polymer header, designed to save a bit of electricity. In terms of efficiency it puts it a little bit ahead of most other heaters on the market.

Typically it will take about 3 to 4 hours to fully heat the pool at a rate of about 3 to 5 degrees per hour. It’s not that much time compared to other heaters, and besides it being more convenient for you, it also means that less power is used to continually heat the water. The less time spent on making the water comfortable, the more it saves on your electricity bill.

Heating Size

A nice benefit of it being a premium, high-cost pool heater is that it should work on pretty much any pool or spa in existence. It’s a universal model designed to fit in as many places as possible, and thus it also has the ability to heat large amounts of water. It’s likely most appropriate, though, for a 40-50 foot pool.


The kind of power and efficiency you get from a pool heater like this does come at a price. At $1,869, the price can be quite steep for what it does. This restricts it mostly to those who have a lot of money to burn, and/or have a rather large swimming pool and want a single unit that can cover everything. It can otherwise be a bit inaccessible to those who are on a budget. But if premium quality is what you’re after, this Hayward pool heater will serve your needs quite well.


There is very little downside to this natural gas pool heater. When this heater gets going, it works very well, and very quickly. You’ll have a warm pool in a matter of hours and you will be able to continuously have a warm pool throughout the year. This heater will surely extend the amount of time throughout the year where you can enjoy your pool. Just be sure that you’re ready to seriously invest in it, since it will take a significant chunk out of your pocketbook. Overall, this heater gets a rating of 4.5 out of 5 stars.

Purchase it online at a great price!

Review Date
Reviewed Item
Hayward 400,000 BTU Natural Gas Pool Heater
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  • ron earl says:

    have a 18ft. 1/2 in ground pool need to know how many cu. ft. of gass req. to run it

    • admin says:

      It’s tough to say without further detail. I’ll assume your pool holds 10,000 gallons (you can modify the following formula depending on your conditions).

      1. Assume pool volume G = 10,000 gallons
      2. Assume 80F desired pool temperature and 60F is the air temperature. Delta T = 80 – 60 = 20F
      3. BTU’s per gallon x Delta T: 8.33 x 20 = 166.6 BTU’s per gallon.
      4. BTU/Gallons x Gallons (G): 166.6 x 10,000 gal = 1,666,000 Total BTU’s.
      5. Assuming you want to warm the pool continuously over two days = 48 hours.
      6. Total BTUs / Hours: 1,666,000 / 48 = 34,708 BTU’s per hour.
      7. (BTU/Hr x 20%) + BTU/Hr: 34,708 x 0.20 = 6,941 BTU’s 6,941 + 34,708 = 41,649 BTU’s per hour.

      You would need around 50,000 BTU gas heater. The more powerful, the faster it will heat your pool.


    do all gas heaters come with electric ignition

  • Kyaw Myat Thu says:

    please kindly reply to me about Hayward S360SX capacity, max: working pressure, inlet/outlet pipe size and filter area?

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