How to Prime a Pentair Pool Pump & Fix High Pool Filter Pressure
If your Pentair pool pump won’t prime or your pool filter pressure is too high, you’re likely dealing with one of the most common (and frustrating) issues in pool maintenance. A pool that isn’t circulating properly can quickly turn cloudy, develop algae, or even cause long-term damage to your pump and filtration system. It might start with low water flow at the returns, or a noisy, overheated pump motor that’s not moving water like it should. When this happens, your first step should be to check whether your pool pump has lost its prime—meaning it’s full of air instead of water and can’t generate the suction needed to circulate water through your system.
Priming your Pentair pump is a relatively easy fix once you know how to do it correctly. In this guide, we’ll show you how to prime a Pentair pool pump step-by-step, including tips for identifying and preventing air leaks that could be interfering with the process. But a properly primed pump isn’t the end of the story. Many pool owners notice that after they fix their pump prime, the filter pressure is still too high—which is a separate issue, but one that's just as important to address.
High pool filter pressure means your water is struggling to move through the filter media, whether it’s sand, a cartridge, or DE (diatomaceous earth). This often points to a dirty filter, a blockage somewhere in the return line, or even an oversized pump putting too much strain on a small filter. We’ll walk you through each of these possible causes and show you how to fix them, with links to filters, media, and pump parts that can help restore proper flow and extend the life of your pool equipment. Whether your issue is air in the system, a clogged cartridge, or simply outdated filter sand, we’ve got you covered.
How to Prime a Pentair Pump
Priming a Pentair pool pump means filling the pump housing with water so it can generate suction. If the pump fills with air instead, it can’t pull water from the pool, causing it to run dry, overheat, and stop circulating properly.
Steps to prime a Pentair pump:
- Turn off the pump at the breaker for safety.
- Open the pump lid and remove any debris from the basket.
- Fill the pump housing completely with water using a hose.
- Inspect the pump lid O-ring, clean it, and apply a silicone-based lubricant. Replace it if it’s cracked or worn. You can find replacements in the pump parts section.
- Secure the lid tightly to prevent air leaks.
- Open all valves connected to the skimmer, main drain, and return lines.
- Turn the pump back on and watch for consistent water flow. It may take a minute or two.
- Observe the system. Once primed, water should move steadily through the returns without bubbles.
If the pump still won’t prime, check for common causes such as a low pool water level, cracks in the suction-side plumbing, or loose fittings. Air leaks are a frequent reason for priming issues, especially if the O-ring is damaged or improperly seated.
Why Your Pool Filter Pressure Is Too High
Once your pump is primed and circulating correctly, check the filter pressure gauge. Normal operating pressure usually falls between 10–20 PSI. If your gauge reads 8–10 PSI above your system’s clean baseline, that’s a sign of restricted flow or pressure buildup within the filter.
Common reasons for high pool filter pressure:
-
Dirty or clogged filter media
Filters naturally collect debris, and over time this buildup reduces flow. This applies to all types: sand filters, cartridge filters, and DE filters. -
Blockages in the return line
Check for partially closed valves, debris in eyeball fittings, or pipe restrictions that may be causing backpressure. -
Air trapped inside the filter
If air is caught in the tank, it can compress and raise pressure. Bleed the air using the filter’s pressure relief valve until water flows out. -
Old or compacted filter media
Over time, sand becomes dense, cartridges clog permanently, and DE grids wear down. Replacing the media can significantly reduce pressure.
-
Pump-to-filter mismatch
A pump that’s too powerful for your filter can overwhelm it, causing constant high pressure. If you suspect this may be the case, consult the Pentair pump guide for equipment sizing tips.
Troubleshooting Guide for High Filter Pressure
| Symptom | Likely Cause | Solution |
|---|---|---|
| PSI is 10+ points above normal | Dirty or clogged filter | Backwash sand or DE, clean cartridge |
| Clean filter, pressure still high | Return line blockage | Inspect and clear return lines and valves |
| Pressure spikes after priming | Trapped air in system | Open air relief valve to release air |
| Weak flow after cleaning | Worn or compact media | Replace sand, cartridge, or DE grids |
Tips to Maintain Prime and Filter Efficiency
- Keep a pressure log to know your filter’s clean baseline PSI.
- Clean or backwash regularly depending on your filter type and usage.
- Inspect pump O-rings and gaskets for cracks or dry rot that could allow air in.
- Fully open all return valves to ensure unrestricted water flow.
- Replace media every 1–3 years based on filter type and condition.
Preventative care can go a long way. Regularly cleaning and inspecting your pool equipment keeps your system running smoothly and helps you avoid issues like high filter pressure or priming failure.
The Bottom Line
If your Pentair pump won’t prime or your pool filter pressure is too high, both problems can usually be resolved with basic troubleshooting and maintenance. Start with the pump: make sure the housing is full of water, all valves are open, and the O-ring is sealing properly. Once primed, check your pressure gauge and clean or replace your filter media if needed. Keep an eye out for air leaks and flow restrictions in the return lines, and make sure your equipment is properly matched for your pool size.
If you’re stuck or unsure what you need, feel free to reach out to our team, at Aqua Pool Supply we're always ready to help you make pool care a little easier and less stressful.
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