How to Descale Your Air Conditioner: A Step-by-Step Guide to the Circulation Method

Companion video click here

Hey there, boaters and DIY enthusiasts! If you’ve been following along, you know I recently tried to shortcut descaling my salon air conditioner with the pickling method. Well, old Murphy’s Law caught up with me, and the quick fix didn’t cut it—the AC was still going press high. So, today, I’m diving into the circulation method to properly descale the unit. Grab your tools, and let’s get to work on keeping that air conditioner running smoothly!

Why Descale Your Air Conditioner?

Air conditioners on boats, especially those using seawater systems, are prone to scale buildup from salt and other minerals. This gunk clogs the system, reduces efficiency, and can cause your AC to overheat or shut down. The circulation method, while more involved than pickling, is a thorough way to flush out scale and restore performance. Trust me, after my recent experience, I’m sold on doing it right the first time!

Tools and Materials You’ll Need

• Shop vacuum
• Borescope (optional, for before-and-after visuals)
• Screwdriver
• Hose clamps
• Clear hoses (for visibility)
• Descaling solution (mixed per manufacturer instructions)
• Bucket
• Oil absorbent pads or “diapers” (to protect your boat’s interior)
• Rags
• Fresh water for rinsing
• Headlamp (for working in tight spaces)

Step-by-Step Guide to Descaling Your Air Conditioner

1. Prep the Area

Start by protecting your boat’s interior. In my case, the salon’s carpet was in great shape thanks to carpet protectors, but I still laid down oil absorbent pads to catch any spills. Remove any carpet protectors and open the hatch to access the salon bilge where the air conditioner is located. You’ll see the seawater in and out lines—two white hoses in my setup.

2. Drain the Seawater System

To minimize mess, drain the raw water system. Head to the engine room and close the seacock for the air conditioner. Use a shop vacuum to suck water out of the sea strainer and hoses. I opened the valve on top of the sea strainer to pull out as much water as possible, which kept seawater from spilling into the salon. Clean out the sea strainer basket while you’re at it, and wipe down the glass with a rag for good measure.

3. Disconnect the Hoses

Back in the salon, remove the hose clamps from the air conditioner’s seawater lines. These hoses can be stubborn, especially if they’ve been on for a while. Slide a screwdriver under the edge to break the surface tension, then twist gently to loosen them. I was thrilled to find almost no seawater spilling out—proof that draining the system first was worth the effort. Repeat for the second hose, and use your borescope to capture a “before” picture of the pipe’s interior if you have one.

4. Set Up the Circulation System

Double-check that all air conditioners and the seawater pump are switched off to avoid any surprises. Connect clear hoses to the air conditioner in reverse flow—meaning the water will flow against the normal direction to dislodge scale more effectively. In my setup, the upper hose (normally the out line) was connected to the pump, and the lower hose (normally the in line) was set to return to the bucket. This reverse flow isn’t mandatory, but it can make a big difference.

Mix your descaling solution in a bucket according to the instructions. I used clear hoses so I could see the gunk coming out, which is both gross and satisfying. Plug in the pump, check for leaks, and let the descaler circulate. You’ll likely see air bubbles and debris right away as the solution starts breaking down the scale.

5. Let It Run

Let the pump run for a few hours—two to four, depending on the scale buildup. After about an hour, I noticed the descaler turning less blue, a sign it was reacting with the salt and gunk. You’ll see floaties and color changes in the solution as it works. Skim off any debris if needed, and keep an eye on the hoses to ensure no leaks develop. I let mine run for four hours, checking at the two-hour mark to confirm it needed more time.

6. Rinse and Reassemble

Once the descaler has done its job, disconnect the hoses. Be prepared for some spillage, especially if the air conditioner is below the bucket. Rinse the system with fresh water to flush out any remaining descaler, and use the shop vacuum to clean up any water in the bilge. Reattach the hoses to the air conditioner, tightening the clamps securely.

Head back to the engine room to reassemble the sea strainer. Place the basket back in, secure the top, and open the seacock to let seawater flow in. I used the valve to help prime the pump, ensuring the system was full.

7. Test the Air Conditioner

Turn on the air conditioner and listen for the pump and unit running. Check for leaks around the hose connections, and dry up any residual water in the bilge. I noticed right away that the unit was running cooler than before—a good sign the descaling worked. Let it run for a while, ideally through a few hot and cold cycles, to ensure everything is tight and leak-free.

8. Final Cleanup

Vacuum out any remaining water in the bilge, and clean up the area. My headlamp came in handy for spotting water in the AC bay. The shower pan under the unit caught most of the condensate, but I made sure no water seeped below the bilge paint. Replace the hatch, reposition the carpet protectors, and you’re done!

Lessons Learned

This circulation method is hands-down more effective than the pickling method I tried before. While it takes more time and effort, the results are worth it—my 16,000 BTU salon air conditioner is running like a champ again. If I’d done this from the start, I could’ve avoided the hassle of a second round of maintenance. With guests coming tomorrow, I’m relieved to have all the AC units working without any awkward explanations.

Final Thoughts

Descaling your air conditioner might seem daunting, but with the right tools and a bit of patience, it’s a manageable DIY project. The circulation method ensures a thorough clean, keeping your boat’s AC system in top shape. If you found this guide helpful, hit that subscribe button and ring the bell for more boating maintenance tips. Got questions or your own descaling stories? Drop them in the comments below—I’d love to hear from you! Until next time, stay cool out there!

Note: This article assumes you have a similar seawater-cooled air conditioning system. Always consult your unit’s manual and take safety precautions when working with electrical systems and chemicals.

Companion video click here