ERR PS on Pentair pool heaters is the pressure switch fault displayed on IntelliFlo and newer panel models, functionally identical to the E05 code on older MasterTemp LED displays. Low pool pump flow rate is responsible for nearly half of all ERR PS faults. A clogged filter, open bypass valve, or failed pressure switch account for the rest.
I see this one constantly at the start of pool season or right after someone installs a new variable-speed pump and doesn't set up the heating schedule right. The heater's not being difficult. It literally won't fire without enough water moving through it, and that's actually a good thing. Ignore it long enough and you're looking at a cracked heat exchanger that'll run you $400 or more just in parts.
Phillips #2 screwdriver, Flat-head screwdriver (large, for panel access screws)
What Does the ERR PS Code Mean?
Think of the pressure switch as a bouncer that won't let the heater fire unless there's enough water moving through. Older Pentair units showed E05. Same fault, different display. Before you go ordering a $45 switch, know that 8 or 9 times out of 10 this is a dirty filter or a variable-speed pump running too slow. I replaced three of these switches last season and honestly only one of them was actually bad.
Most Likely Causes
Based on aggregated repair data, here is the probability breakdown for this error code:
Pool pump running at too low an RPM to achieve minimum flow through heater40%
Clogged pool filter increasing system resistance24%
Heater bypass valve open or partially open14%
Air trapped in the plumbing upstream of the heater12%
Pressure switch failure10%
Symptoms You May Notice
ERR PS flashing on the digital display the moment the thermostat calls for heat
Heater fires up, you hear the ignition click, sometimes even see the flame catch for a second or two, and then it just shuts right back down with the code showing
Pool water staying stone cold even though the heater looks like it's been running for hours
ERR PS showing up on your IntelliTouch or EasyTouch automation screen where the water temperature should be
Pressure switch audibly chattering and heater cycling on and off rapidly before locking out completely
Can you reset a Pentair poolheater to clear the ERR PS code?
Hit the Mode button to power the heater off, wait a full 60 seconds, then press it again to restart. If you're running IntelliTouch or EasyTouch, go to your main panel and toggle the filter pump circuit off for 30 seconds, then back on. That forces the heater and pump to re-handshake and re-read flow. Watch for the startup self-check. If ERR PS comes right back, the flow issue isn't fixed yet.
Tools Required for Diagnosis
Phillips #2 screwdriverFlat-head screwdriver (large, for panel access screws)Digital multimeter with continuity modePool filter pressure gaugeGarden hose with spray nozzle (for cartridge filter cleaning)Channel-lock pliers (for pump lid removal)
Diagnostic Checklist
Follow these steps in order. We start with the easiest external fixes before opening up the machine.
ComponentComponent Under Test
Expected Range0–1 ohms
ConditionIf Open (OL) or infinite, replace component.
Replacement Parts
If your diagnostic testing proves the component has failed, you will need a replacement. We recommend OEM parts over aftermarket for water-handling components.
Part Name
OEM Number
Estimated Price
Pressure switch42001-0060S · $25–$60
42001-0060S
$25 – $60
Frequently Asked Questions
What is the difference between ERR PS and E05 on Pentair heaters?
Basically the same warning in two different languages. Older MasterTemp boards used a simple 3-digit LED that could only display numbers, so low flow showed up as E05. When Pentair updated the control boards to talk to IntelliFlo pumps and modern automation systems, they switched to alphanumeric displays that can actually spell out the fault. So ERR PS replaced E05. Same root cause, same fix. If you search either code, you're dealing with the exact same pressure switch fault. Don't let the different display throw you off.
What RPM should my variable-speed pump run at for a Pentair pool heater?
There's no universal number because every pool's plumbing resistance is different. A heater 10 feet from the pump needs way less RPM than one at the end of a 100-foot run with four elbows. That said, 2,400 RPM is where I'd start for most setups. If ERR PS clears at 2,400, great. If not, bump to 2,600, wait 30 seconds, see if it fires. Work your way up in 200-RPM increments. I've set some installs to 3,200 RPM for the heating program because the plumbing run is just too long. Once you find the minimum that works, add another 200 RPM as a buffer so the switch doesn't flutter.
Can ERR PS cause damage if I ignore it?
Short answer: the code itself won't damage anything because the heater won't fire. But here's the thing. If the pressure switch is borderline, maybe the diaphragm's just starting to fail, it might close just long enough for the heater to light and then immediately open again. That means the burner cycles on and off, which hammers the igniter, wears out the gas valve, and causes thermal stress in the heat exchanger. A new heat exchanger for a MasterTemp 400 is around $400 in parts alone, plus labor. Don't ignore a fluttering pressure switch. Fix the flow issue.
How do I know if my pressure switch is bad or if the flow is just too low?
Do the multimeter test. It takes five minutes and it'll tell you for certain. If your return jets are blasting strong, filter pressure is normal, all your valves are set right, and the switch still reads open on the meter with the pump running at 3,000 RPM, that's a bad switch. A customer of mine had already bought the switch before I got there, assumed that was the problem. Turned out someone had cracked a bypass valve open six months earlier. He had a perfectly good $45 switch sitting in a box. Test first, buy parts second.
Will ERR PS clear itself once I fix the water flow?
Usually yes, the heater will try to fire again within a minute or two once it senses enough flow. But a lot of times it sits in lockout and needs a manual reset. Just cycle the Mode button off and back on at the heater panel. Wait a full minute between off and on. If you're on an automation system, cycle the filter pump circuit at the main controller too. That fresh handshake usually clears it right up. If it throws ERR PS again immediately after restart, the fix didn't take and you've still got a flow problem somewhere.
I already replaced the pressure switch and I'm still getting ERR PS. Now what?
Honestly, this is the most common callback I get on pool heater jobs. New switch goes in, code comes back, and now the customer thinks I sold them a bad part. Almost every time the real issue was never the switch to begin with. Could be the pump speed, a loaded filter, a cracked-open bypass valve, or even a partially closed return valve downstream of the heater. A new switch only fixes the problem if the old switch was actually bad. Go back through the flow diagnostics from the top and test each step. The answer's in there somewhere.