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Your Guide To Choosing The Best Inground Pool Heater

Updated on February 14, 2016

What do you look for in an Inground Pool Heater?

Pool heaters are quite literally a gift from the world of science and technology to people who love swimming but cannot stand the cold water. Swimming in a cold pool when it isn’t summer weather is not always as fun as it looks. Most of the time is spent gasping for breath as an involuntary reflex after the sudden temperature drop around you. There is also always the risk of getting a cold especially when swimming in cold water at night or in cold weather. I have a friend who has completely refused to set as much as a toe into water that is not at the very least 75°F.

To accommodate this friend’s preferences as well as my own, I set out to find a great inground pool heater for my pool. Unlike older methods of water heating including wall heaters and using covers, inground pool heaters are amazing due to their fast action, proper heat distribution and the icing on the cake, affordability. The two series that caught my eye in the search are the Pentair Master Temp and the Hayward Universal H-series pool heaters.

Review of 2 of the best inground pool heater series

Both of these inground pool heater series are categorized as low NOx emitters. NOx refers to Nitrogen Oxide gas that is produced when natural fuels are burnt at high temperatures. This gas is poisonous and high emitters are usually discouraged. This makes the Pentair Master Temp and Hayward Universal great options due to their low emission ranking. In addition to their environmental friendliness, they have some pretty amazing features. Below are a few of my favorite and least favorite things about these series with a few model examples from each. This should help you find the perfect inground pool heater for you in case you are looking for one now or in the near future.

a) Pentair Master Temp Pool Heaters Review

These are products of Pentair Company which is well known for their highly efficient and reliable aquatic systems and amazing pool accessories. Their Master Temp pool heating series is one of the best in the market. Below are some of my favorite features of the models in this series.

General features of the series

  • Tough rust proof exterior- This is an advantageous feature that is aimed at increasing the durability and resilience of the heater. This is because exposure to air and low pH water promotes rusting and this would reduce the longevity of the product if the rust proof feature was absent. It also maintains the aesthetics around your pool. The last thing anyone wants is a rusty old machine next to their clean pool.
  • It has low NOx emissions- What this means is that there is less Nitrogen Oxide gas being released from the fuel burning process. This makes it safe to set up near the pool area without the risk of inhaling poisonous fumes.
  • Noise cancelling design- The inground pool heaters in the Pentair Master Temp pool heaters series are all fitted with noise cancelling muffs that keep the machine whisper quiet. This is a major advantage to pool users as they get to enjoy the peace and serenity of the pool or deck without being interrupted by any annoying noise.
  • Has a manual gas shut off- This feature makes it possible to turn off the gas supply to the inground pool heater. It comes in handy when there is need for maintainance or repair. It is also useful when the pool user wishes to use the pool unheated.
  • Has a rotating digital display screen- The screen acts as an interface that allows you as the user to make different selections to adjust the functions of the pool heater. These include turning it on and off and selecting the temperature rise you want for your pool water. The rotating ability makes it convenient to use from any side.

Popular models from th Master Temp series

  1. Pentair 460736

In addition to the general features above, the Pentair 460736 model has the following unique features:

  • It is 400,000 BTU in terms of pool heater size. This means that for every 400,000 pounds of water there is a one degree temperature rise per unit time.
  • It runs on natural gas. This makes it more environmental friendly and in some places it is more affordable than liquid propanol.

2. Pentair 460737

Features unique to this model include:

  • It is four hundred thousand BTU large.
  • It runs on liquid propane as the fuel of choice. This is in its own way an advantage due to the high combustibility of propane as a fuel. This means than heat is generated much faster than in pool heaters that run on natural gas. Propane also has less corrosive effects on the engine parts than other fuels.

Pros and cons of these models


  • They are durable due to the rust proof feature.
  • They are quiet.
  • They are efficient with high BTU levels
  • They are environmental friendly
  • The display screen makes the machine user friendly


It may be expensive to keep buying fuel to keep the heater running.

Difference between ASME and the two Pentair models

ASME heaters are a product of Hayward Hydraulics Company under the commercial pools universal H-series. As a pool heater, it is larger than the two Pentair models above and has a BTU rating of 500,000. The ASME heaters also have additional features absent in the Pentairs including a pressure relief valve, dual voltage conversion and independent gas and electricity connections on either side. This model however, does not have the manual gas shut off feature. In its place is an easily adjustable gas valve. It is also more suitable for commercial installation in large pools and may not be appropriate for smaller domestic pools.

b) Hayward Universal H-Series Pool Heaters Review

The Hayward Universal H-series pool heaters are among the best in terms of performance and efficiency. This series has many different models but the difference is usually in terms of BTU size. Below are a few of the best general features shared by most of the models.

General features of the series

  • Low NOx emissions- This feature makes it an environmentally friendly option and one that is safe for installation near the pool.
  • Uniform water velocity design- This is achieved by the water channels on each side of the heater. It works by ensuring that the water moves through the machine at uniform speed for an even heating effect.
  • Corrosion and rust proof interior and exterior- The material used to make the water channels is resilient against corrosion by the low pH salty water that passes through it. The exterior is made from different material but equally as resistant corrosion and rusting. This makes it possible to set up close to the pool without worrying about effects of water splashing onto it.
  • Uses a cupro nickel heat exchanger- This is the part of the heater that does the actual heating of the water. Nickel is a great conductor of heat. This ensures that the water is heated quickly and efficiently. The plate is also designed in such a way that there is a totally managed exchanger flow. This feature ensures efficiency and uniformity in heating.
  • They use a patented header bypass design- This feature is unique to the Hayward Universal H-series pool heaters. It promotes the heat exchange process for more efficient heating using much less fuel than ordinary heating systems.

Popular models from the Hayward Universal H-Series Pool Heaters

  1. Hayward H400FDN

The H400FDN model has a 400,000 BTU measurement. This makes it ideal for both commercial and domestic pools. It runs on natural gas which is usually the less expensive option. The NOx emissions from the fuel combustion are also very low.

2. Hayward H400FDP

This model also has a BTU rating of 400,000 units. Unlike the H400FDN, the H400FDP runs on liquid propanol. This makes it more efficient as the fuel burns faster and produces more energy than natural gas.

Pros and cons


  • The Hayward Universal H-series pool heaters are environmentally friendly with the low NOx emissions feature.
  • They are durable
  • The rust proof and corrosion resistance increases efficiency and maintains aesthetics.
  • It is highly efficient in water heating.
  • It is energy conserving and this is achieved by the patented header bypass feature.
  • It is easy to install, use and maintain.
  • It provides uniformity. This is in terms of pool water temperature.


There is a high cost of running. This is because it runs on exhaustible fuels. This means that there is need to regularly refill after the fuel is used up.

How to make sure you get the right size for your pool

One of the most important things to remember is that with inground pool heaters size really does matter; both pool size and heater size. The size of the pool heater is measured in British Thermal Units (BTU) where one BTU can rise the temperature of one pound of water by one degree. If you get a heater that is too big for your pool you will end up with an overheated pool and a lot of energy wasted. If you get a heater that is too small for your pool in terms of BTU you will end up with an unevenly heated pool with some parts colder than others. Below are five ways you can make sure you get the right BTU size for your pool.

  • Consider the pool surface area and depth not shape- These measurements help you to calculate the volume of water that your pool can hold. This is important in determining the appropriate size of inground pool. With irregularly shaped pools, divide into sections of regular shapes to take more accurate measurements.
  • Consider the temperature rise you want- Do you want it lukewarm or Jacuzzi hot? This is important when deciding the BTU size for your pool. Logically, the higher the BTU size the faster and hotter the pool water becomes.
  • Consider fuel price- This is determined by the fuel type. You can either use liquid propane or natural gas. If the model you choose runs on the more expensive option available around you, you will save yourself more money by choosing smaller BTU sizes. This is because the larger sizes use a whole lot more fuel and this means that you end up spending a lot more than you should on keeping it running.
  • Consider efficiency- This is given as a percentage that compares the amount of heat generated by a single BTU unit and transferred to water. Larger inground pool sizes are more efficient and this means that more heat is transferred to water. Convectional currents between cold and heated water ensure that the heating is evenly distributed.
  • Consider how fast you want your pool heated- Inground pool heaters with high BTU values usually heat faster than smaller ones. It is for this reason that people choose to ‘oversize’ their pool heaters. This is where the heater is much larger than the recommended size for the specific pool. People do this in an attempt to get faster and more distributed heating. Although effective, it is much more expensive than other options which despite being slower are just as effective.


Bottom line

It goes without saying that making the right choice of inground pool heater for you can be a bit tricky especially with so many models available in the market. The most important things to consider are price of purchase and maintenance, heating efficiency, environmental friendliness as well as ease of installation. The Pentair Master Temp and the Hayward Universal H-series pool heaters have some pretty amazing features with many pros and few cons. Therefore, whether you are setting up a new pool or need a heater for an old one, these two inground pool heater series are a pretty good place to start in your search for the right one.


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    • FlourishAnyway profile image


      2 years ago from USA

      This makes me wish I had an in ground pool!


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