What Is a Perc Test and Why Do NH Buyers Need One Before Building?

🏡 What Is a Perc Test and Why Do NH Buyers Need One Before Building?

If you’re looking at land in Plymouth, Wentworth, Rumney, Campton, Thornton, or anywhere across Central NH, one of the most important steps before building is getting a perc test.

This test determines whether the soil can support a septic system — which is crucial in areas without public sewer.

Here’s what NH buyers need to know.

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What Is a Perc Test?

A percolation (perc) test measures how quickly soil absorbs water.

NH septic systems require soil that drains at the right speed — not too fast, not too slow.

A licensed septic designer or engineer performs the test by:

✔ Digging test pits

✔ Filling them with water

✔ Measuring absorption rate

✔ Evaluating soil type and depth

The results determine what type of septic system is allowed.

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Why Perc Tests Matter in New Hampshire

Most rural NH towns do not have public sewer.

Your ability to build a home depends on the property passing a perc test.

A good perc test means:

✔ A standard septic system is allowed

✔ Lower construction cost

✔ Faster approval through the state

✔ Fewer long-term maintenance issues

A poor perc test may require:

✔ A more expensive engineered system

✔ Redesigning the building site

✔ Additional testing

✔ In some cases — the land may not be buildable at all

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Typical Perc Conditions in Central NH

Central NH soil varies widely:

Plymouth & Ashland: Mixed soils, often good drainage

Rumney & Campton: Rocky, ledge areas — may need engineered systems

Wentworth & Thornton: Deeper soils, good for standard systems

Mountain or riverfront lots: Higher water tables, more testing needed

Always review perc results before committing to land.

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What Happens After a Perc Test?

If the soil passes, the septic designer creates a:

✔ Full septic design

✔ Site plan

✔ State approval package

This is submitted to the NH Department of Environmental Services (NHDES) for approval.

Once approved, the system can be installed anytime.

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Q&A

Q: Can you do a perc test year-round?

A: Yes, but frozen ground or high spring water tables can affect results.

Q: Does a failed perc test mean the land is worthless?

A: Not always — an engineered system may still work, just at a higher cost.

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Keywords

nh perc test, new hampshire septic rules, plymouth nh land buyers, campton nh building tips, rumney nh soil tests, thornton nh septic design, central nh buildable land

Jim Johnson — Real Estate Agent

58 NH Route 25A

Wentworth, NH 03282

P: (857) 249-7392

W: www.JimJohnsonRealEstateAgent.com

Licensed New Hampshire REALTOR® with Three Hills Real Estate Services

Broker Email: info@ThreeHillsRES.com

Broker Website: www.ThreeHillsRES.com