How do you level a sinking air conditioner pad?

What causes an AC unit pad to sink?

There are a few potential causes for an air conditioner pad sinking over time:

• Improper installation: If the pad was not properly leveled and supported during the initial AC unit installation, it can settle and sink unevenly over time as the weight of the unit pushes down.
• Weak soil: If the pad was installed over loose, sandy, or wet soil, the soil can compact and give way under the weight of the unit, causing the pad to sink.
• Erosion: Outdoor AC unit pads can erode around the edges due to rain, sprinklers, etc. This can undermine the soil support and lead to sinking and tilting.
• Lack of maintenance: Pads require occasional maintenance to fill settling soil, replace eroded areas, and keep level. Lack of this care over years can result in gradual sinking.
• Age and wear: Concrete pads can slowly crack, crumble, and compact after years of use, leading to uneven settling.

The most common reasons are weak support soil and lack of periodic maintenance on the pad. But any of these factors can contribute to a sinking air conditioner concrete slab over time.

How to tell if your AC unit pad is sinking

There are a few clear signs that your outdoor air conditioning unit has a sinking pad:

• Uneven unit: If the body of the AC unit is no longer level, this indicates the pad has likely sunk on one side.
• Tilting or sagging: Significant sinking will cause the unit to tilt to one side or appear to sag in the middle.
• Door/cover alignment issues: If doors or panels on the unit are sticking or misaligned, the unit is likely no longer square due to pad sinking.
• Condenser leaning: The large condenser fan may appear tilted or crooked if the pad has sunk.
• Cracks or gaps: Check the concrete pad for new cracks, gaps, or uneven sections that indicate settling.
• Water pooling: Low spots in the pad will hold rainwater and sprinkler runoff rather than draining properly.

Any of these signs indicate your AC unit’s concrete slab should be evaluated and potentially leveled to restore proper support. Ignoring sinking pad issues can put added strain on the unit and create operational problems.

Dangers of an unlevel air conditioner pad

Letting an AC unit concrete slab sink over time without corrections can lead to a number of problems:

• Strain on components: An unlevel unit puts stress on the compressor, fan motor, and refrigerant lines.
• Condensate drainage issues: Sinking can prevent proper condensate drainage, leading to unit shutdowns.
• Shortened service life: The added stresses shorten the lifespan of the unit if left uncorrected.
• Compromised operation: Performance can suffer as the system cannot cycle properly or maintain refrigerant flow.
• serializer damage: Allowing the heavy AC unit to sag without support can damage the bottom serializer.
• Safety hazards: Risks include tripping, unit shifting/falling, water damage, or refrigerant leaks.

The continual strain of an unlevel air conditioner unit can lead to premature breakdowns, leaks, electrical shorts and other expensive repair issues. It’s important to fix sinking pad issues promptly before operation or safety are compromised.

How to level a sunk air conditioner slab

Here is a step-by-step guide to straightening and leveling a sunk air conditioning unit pad:

1. Disconnect electrical power to AC unit for safety.
2. Remove any obstructing landscaping, grilles or housing around the pad.
3. Use a string level or laser level tool to assess how much and where pad has sunk.
4. Dry pack mortar mix under sunken side(s) or areas 1-2 inches at a time.
5. Check level frequently and let mortar fully cure before adding more.
6. For larger gaps, insert solid concrete bricks or pavers before packing mortar.
7. Pack mortar into any holes or openings in the original pad.
8. Feather out mortar around raised sections to create a smooth, gradual slope.
9. Recheck entire pad with level and make any final adjustments.
10. Allow mortar to fully cure before reconnecting power.

Going slowly and checking the level often are key to getting the slab back to level without over-raising any side. Some shimming under the AC unit feet may help get it seated evenly on the leveled pad.

Tips for preventing sunk air conditioner pads

To avoid sinking pad issues in the future, keep these tips in mind:

• Install on well-draining soil or use gravel fill under the slab.
• Make sure pad is large enough for the AC unit size and weight.
• Reinforce pad with rebar or mesh for added tensile strength.
• Slope pad slightly to facilitate condensate runoff.
• Shim and level AC unit carefully when installing.
• Periodically check pad and patch eroded or settled areas.
• Consider installing impression pads under AC unit feet to distribute weight.
• Ensure outdoor sprinklers are not excessive and eroding pad.
• Seal pad cracks to limit water intrusion and soil settling.

Proper installation and periodic pad maintenance can add years of life to an AC concrete slab and help prevent sinking or soil settling issues.

When to call a professional for help

Here are some instances when the challenge of leveling an air conditioner slab may require calling in a professional:

• The pad has sunk or tilted significantly (over 3 inches).
• There are large gaps, cracks or deterioration in pad.
• You determine the original installation or soil is unstable.
• Leveling efforts are unsuccessful.
• The unit or pad has shifted far out of alignment with the home.
• There are any refrigerant or condensate leaks.
• You lack the tools, materials or ability to safely lift the AC unit.

With major sinking, soil heaving, or alignment issues, a technician may recommend replacing the entire pad. Professionals also have the equipment needed to safely lift and re-secure the heavy AC units after leveling the pad.

Costs to level a sunken air conditioner pad

Typical costs to level a slightly sunk AC unit pad:

• DIY using mortar and a rental concrete mixer: $150 – $300
• Professional concrete contractor: $200 – $700

For more extensive jobs involving AC removal, new piers, or full pad replacement expect costs of:

• Adding piers/foundations: $500 – $1,500
• Full pad replacement: $1,000 – $3,000

Get multiple quotes before hiring any contractors. Leveling costs can vary based on local rates, size of the job, and site conditions. With proper installation and maintenance, sinking pads can often be avoided.

Conclusion

Letting an outdoor air conditioning unit pad sink or settle out of level can lead to operational issues, wear and tear on the AC system, and potential safety hazards. Homeowners noticing signs of uneven sinking should take steps to raise and re-level affected areas of the pad. For major adjustments or jobs involving integrated foundations, a concrete or HVAC technician may be needed. But for typical slight sinking, applying mortar layers and routinely checking with a level offers an affordable DIY solution. With careful installation and periodic maintenance, costly full pad replacements can usually be avoided. Addressing minor pad settling promptly before it worsens protects your AC investment and prevents much larger repairs down the road.