How to Diagnose Complex Pool Equipment Issues

When you’re first starting out in pool service, it’s all about keeping water clear and customers happy. But as your experience grows, you realize the real game-changer: being able to diagnose and fix complex pool equipment issues.

It’s one thing to balance water. It’s another thing entirely to walk onto a property, troubleshoot a failing pump or heater, and save your customer a $2,000 replacement.

Strong diagnostic skills don’t just save your clients money — they position you as a true expert and allow you to charge a premium for your work.

Let’s dive into what separates good pool care techs from great ones when it comes to diagnosing equipment issues.

The Big 3 Systems Every Pool Pro Needs to Master

When something isn’t working right, start by thinking in three categories: Circulation, Sanitation, or Heating. Breaking it down this way speeds up troubleshooting — and makes you look sharp in front of clients.

Circulation System (Pumps, Filters, Valves)

Common Symptoms

• Weak flow or no flow
• Visible air bubbles in pump basket or return jets
• High or low filter pressure readings

How to Diagnose Circulation Problems

• Pump Issues
  • Loud screeching = bad motor bearings.
  • Low flow + air bubbles = suction leak (usually lid O-ring, pump housing, or suction-side plumbing).
  • Rapid pressure drop after startup = clogged impeller or collapsed suction line.
    
• Filter Problems
  • High pressure even after a clean = internal damage (torn grids, broken manifolds).
  • Low pressure + poor filtration = bypassing inside the filter (broken internal plumbing).
    
• Valves
  • Stiff multiport valve? Cracked spider gasket.
  • Suction side valve leaks? Air intrusion issues.

Quick Troubleshooting Steps

1. Check skimmer and pump baskets for clogs.
2. Inspect pump lid O-ring and tighten fittings.
3. Verify filter pressure — note any sudden changes.
4. Run system isolated by zone if needed (e.g., spa vs. pool suction).

Sanitation Systems (Salt Cells, Chlorinators, UV/Ozone)

Common Symptoms

• Poor chlorine levels despite dosing
• Salt system throwing “Low Salt” or “Cell Error” warnings
• ORP systems not maintaining target levels

How to Diagnose Sanitation Problems

• Salt Cells:
  • Visually inspect for scale buildup.
  • Test voltage across cell (compare to the manufacturer specs).
  • Clean with proper acid dilution if scaling is visible.
    
• Chlorinators/Feeders:
  • Check for clogged lines or stuck feeder valves.
  • Inspect chemical supply tubing for cracks.
    
• UV/Ozone Systems:
  • Confirm bulb lifespan or ozone output.
  • Check sensors and verify they’re calibrated.

Quick Troubleshooting Steps

1. Test salt levels independently of the system’s reading.
2. Perform physical inspection of cells and tubing.
3. Reset sanitation control systems after cleaning.

Heating Systems (Gas Heaters, Heat Pumps, Solar)

Common Symptoms

• Heater fires up briefly, then shuts down.
• Heater won’t ignite at all.
• Pool temperature doesn’t rise properly.

How to Diagnose Heating Problems

• Flow Issues
  • Check filter pressure. Heaters need adequate flow to stay lit.
  • Verify bypass valves are correctly positioned.
    
• Ignition Problems (Gas Heaters)
  • Test gas pressure at the heater manifold.
  • Clean or replace flame sensor or ignitor.
    
• Control Board or Sensor Failures
  • Use error codes to guide inspections.
  • Inspect thermistors for damage or corrosion.

Quick Troubleshooting Steps

1. Clean the filter before doing anything else.
2. Check pressure switches and water flow sensors.
3. Inspect and clean igniters or flame sensors.
4. Verify the correct voltage at the control board if necessary.

My Pro Tip: 90% of heater “failures” are actually flow issues, not true mechanical breakdowns.

The Diagnostic Mindset: How to Solve Pool Problems Like a Pro

Being a good diagnostician isn’t just about part knowledge — it’s about how you think.

Adopt a Step-By-Step Troubleshooting Process

1. Observe Carefully.
   • Listen for unusual sounds, watch flow patterns, feel for vibrations.
     
2. Isolate the Problem.
   • Break the system into sections. Don’t test everything at once.
     
3. Test Systematically.
   • Use gauges, multimeters, and flow meters.
     
4. Verify the Repair.
   • After fixing, double-check the system under normal load.

Tools Every Pool Care Truck Should Carry

You don’t need a full-blown electrician’s kit — but you should always have these on hand:

• Digital multimeter (for voltage and continuity testing)
• Pressure gauge (with T-adapter for pump/filter diagnostics)
• Basic flow meter
• Pocket thermometer
• O-ring lubricant
• Acid wash kit (for salt cell cleaning)

My Pro Tip: Having the right tool often saves an hour of guesswork.

When Water Chemistry Wrecks Equipment

Bad water isn’t just ugly — it can ruin or destroy your equipment.

How Chemistry Problems Damage Systems

• High Calcium
  • Scales heaters, blocks salt cells, shortens pump life.
    
• Low pH
  • Corrodes heat exchangers, pump seals, and metal valves.
    
• High Stabilizer (CYA)
  • Causes low ORP levels even when free chlorine reads “fine.”
    
• High TDS (Total Dissolved Solids):
  • Wrecks sensor accuracy and stresses heater systems.

My Pro Tip: If you’re diagnosing a heater failure in a pool with scaling issues, test calcium first before blaming the unit itself.

Communicate and Document Like a Pro

Being able to explain the issue is just as important as fixing it.

Best Practices

• Always take photos of failed parts or error messages.
• Document chemical readings when related to the equipment failure.
• Keep simple, plain-English service reports.

Example Service Report Structure

• Problem Observed
  Heater not firing, system pressure low.
• Action Taken
  Filter cleaned, impeller inspected for clogs, flow restored.
• Resolution
  Heater fired normally after restoring proper flow.

The Wrap-Up: Build Trust Through Better Diagnosing of Issues

Advanced trouble-shooting turns you from “the pool guy” into the pool expert.

It’s what earns you referrals, customer loyalty, and higher ticket jobs. 

Anyone can vacuum a pool, but few can confidently diagnose why a heater is locking out or a salt system isn’t producing chlorine. I can’t tell you how many accounts I’ve picked up because their “pool guy” couldn’t figure out the problem. 

Advanced troubleshooting skills take time to build, but they’re one of the biggest things that separate a $85-a-month technician from a well-paid and trusted professional. 

Keep learning, invest in diagnostic tools, and approach every equipment problem with a clear, step-by-step process because at the end of the day, solving tough problems isn’t just about saving the pool — it’s about building a reputation you can take to the bank.

Read Next:
— Pool Care Chemistry 101: How to Troubleshoot Common Pool Water Issues
— Scaling Your Pool Business: From Solo Operator to Managing a Team
— Marketing Strategies for New Pool Service Businesses

Main Image: Backyard in-ground swimming pool maintenance. Photo Credit: Tomasz Zajda / Adobe Stock Free / License

Nick Preston

Nick Preston is the owner of Best Coast Pools and a guy who believes great businesses are built on great systems — and even better relationships. He’s been in the trenches of service, operations, and growth and now his passion is helping other pros build businesses — and lives — that they’re proud of.

Posts by Nick Preston