Pentair MasterTemp 400 Common Problems


We know exactly how you would feel when you have a pool party at home, and you get to know that your pool heater is not working efficiently. Anybody would feel annoyed and panicked. But calm down as we have brought you the solutions for common problems that you face in Pentair MasterTemp 400.

Problems like Off and On issues with your pool heater, water flow not working efficiently, the position of a heater, Temperature display, etc. These problems can be solved with just minor steps. Let’s begin and troubleshoot step by step.

Pentair MasterTemp 400 Common Problems


Ignition Problem

So many customers have mentioned that they have a problem with the ignition of the heater. Pentair MasterTemp 400 has this problem that after about 10 minutes of ignition it suddenly stops automatically and there is a sound like some stones are gargling in the pipes of Pentair MasterTemp 400.

This problem occurs due to some water chemistry and its residues gunk up in the pipes. Basically, this problem occurs when there is no proper water flow, then Pentair MasterTemp 400 gets too hot from inside that it shuts itself off.


First, make sure that your heater is turned on properly. Secondly, check if the temperature is set correctly. If these are not the problem, make sure that the pilot is turned on properly, if not, then check the gas supply is proper.

Do check that the pilot pipe is not clogged. This problem can be eliminated if you clean the water. Make sure that the heater is consuming soft water. If your heater uses hard water then residues can block up the pipe, and the heater will turn itself off.

Positioning the Heater

Some of the customers face problems with the positioning of the headers through which water flows in and out of the heater, and the question in their mind comes what if we have to take out everything from the heater and fix it again according to the pool positioning? But the good news is this can be fixed according to the area where your pool is located. It is just simple and easy.


If the headers of the heater are on the right, but you need them to be on the left side according to the position of your pool then what you have to do is “Rotate.” Just Rotate the heater to the left side, and the headers will move to the left.

Now rotate the top board where the button panel is so that Pentair MasterTemp 400 works properly again. You don’t have to physically take out everything inside and then put it back.

Not Heating Properly

What’s the point of having a heater when it’s not heating? Many customers complained that our pool/spa heater is not working properly. This is a common problem seen in Pentair MasterTemp 400, but this can be surely corrected.


The troubleshooting is easy, you have to make sure the state you live in isn’t too cold because Pentair Mastertemp 400 works with heat pumps which means that it doesn’t use propane gas but consumes heat from the atmosphere. If the atmosphere is cold enough, then it would be difficult for Pentair MaterTemp 400 to create heat.

If this is not the reason then check the pool heater size; it should be according to the size of your pool need. If it is undersized, there will be a problem with heating. You should also inspect your Thermostat settings and set them to a higher temperature. In some cases, the thermal regulator needs to be changed.

Temperature Display

In some cases, a heater fails to display the correct temperature. This is also a common problem that is seen in Pentair MasterTemp 400. This can be sorted out easily.


You will need to change the thermostat if you see any fluctuations in a temperature display. Remove the panel behind the headers. If you observe keenly, you will see a thermostat just above the high limit switch. Take it out by pulling it with the pressure required with the spring attached to the thermistor. Now place a new thermostat carefully and place the spring back in the right position.

Low Water Flow

For heaters to operate efficiently it is necessary that the pool system maintain the flow of water. If the water level is low then it would be difficult for the heater to work properly. Check to maintain water levels by keeping some points in mind.


Check if the filter is cleaned or not. If the filter is cleaned and does not show PSI at a high level, then check the pump’s strainer basket. If it is dirty, then clean it with a hose and make sure that there are no cracks at the lid of a basket.

The most important point to keep in mind is that the sensor is not defective. Test the voltage reading on the pressure switch with help of a multimeter.


Why is Pentair Heater not working?

There could be many reasons for this. The most common reason is maybe the filter is not cleaned properly. Clean the water filter every now and then.

How long Pentair heater should last?

An average pool heater lasts for around 8 to 11 years. So, Pentair heater can last for upto 11 years. The pool heater can last longer if maintained properly by keeping its items maintained and filter clean.

How do I reset my pool heater?

There is a control panel on the pool heater, put that on a stand-by. This can be done by pressing the up and down button. If some error occurs, then fix that problem first; otherwise, pool heater won’t reset.


First of all, keep the pool water’s chemicals balanced and clean the heater so that it won’t stop working due to the gunk stuck in it. Make sure that while installing Pentair MasterTemp 400 everything is perfectly fitted.

Minor problems like the Thermostat changing heater rotation etc can be done easily by yourself at the place where you have Pentair Mastertemp 400, but if some problems cannot be solved by you, then you can take help from a licensed installer.

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