Buying property in Costa Rica: check the septic system first

When you buy a home, a villa or a small hotel in Costa Rica, the wastewater system is easy to overlook. It is buried, it is not in the photos, and it usually works fine on the day of the visit. Yet in many beach towns there is no public sewer, so every property treats its own wastewater on site, with a septic tank or a small treatment plant.

A failing system means odors, wet patches in the garden, complaints from neighbors and, for a business, problems with the Ministry of Health. Fixing it after the sale can be expensive, and sometimes the lot simply does not have room for a larger drain field. This guide explains what to check before you sign.

Why it matters

Three reasons make the wastewater system a real due-diligence item in Costa Rica:

• No sewer in many coastal areas. Homes rely on septic tanks with drain fields; hotels and condominiums often run their own treatment plants.
• Seasonal stress. A beach property can sit half empty for months and then fill up in high season. A system sized for a couple may not cope with a full house of guests.
• Clear rules that come with the property. The permits and obligations of a treatment plant stay with the property and its operator. If the reports are behind or a permit has lapsed, the new owner inherits the problem.

There is also a practical reason. Correcting a wastewater system usually means digging up gardens, driveways or pool decks, and a hotel may have to limit occupancy while the work is done. Knowing the condition of the system in advance lets you negotiate the price, plan the work for the low season or walk away in time.

What to inspect

Homes and villas with a septic tank

Since April 2020, home septic systems that discharge into the ground are governed by Executive Decree 42075-S-MINAE. Among other things, it requires:

• a septic tank with a useful volume between 1.2 and 5 cubic meters, sealed and watertight, with baffles or tees at the inlet and outlet;
• a drain field made of infiltration trenches, sized from at least two infiltration tests on the site;
• soil with an infiltration rate between 2 and 24 minutes per centimeter, on slopes no steeper than 30%;
• the water table at least 1.5 meters below the bottom of the trenches;
• the drain field in green areas, never under parking, driveways, patios or slabs;
• minimum distances to property lines, buildings, slopes and drinking water tanks.

The decree defines a septic tank as a solution for flows of up to 5 cubic meters per day. A large villa rented to many guests, or several houses on one lot, may exceed that and need a different system.

On site, an engineer should:

1. Open the tank and measure sludge and scum.
2. Check the inlet and outlet tees and the vent.
3. Walk the drain field and look for wet or unusually green areas.
4. Confirm that roof gutters and patio drains are not connected to the sanitary line.
5. Compare what is built with the approved plans, if they exist.

An improved septic tank, with an upflow anaerobic filter after the tank, treats the water better and protects the drain field. See our page on improved septic tanks (in Spanish) or our English overview of septic systems in Costa Rica.

Hotels and condominiums with a treatment plant

For a plant, the questions are both technical and administrative:

• Is the plant operating as designed, or have parts been bypassed?
• Is there an operator, an operation and maintenance manual and a logbook? Decree 33601-MINAE-S requires a wastewater logbook with routine measurements, sampling, incidents, changes to the system and sludge management.
• Does the plant still match the current occupancy, or has the property grown since it was built?

If the plant is undersized or poorly built, it can often be redesigned rather than replaced. That is what our treatment plant redesign service does (page in Spanish).

Permits to ask for

Ask the seller for copies of these documents. Which ones apply depends on the property.

A few details matter:

• Report frequency. Under Decree 33601, plants with an average flow up to 100 m³/day report every six months; larger ones every three months. A property that only operates part of the year has its own rule.
• Discharge permits last up to ten years and carry a quarterly fee. Two unpaid quarters can lead to revocation.
• Renewing a sanitary operating permit requires the operational reports to be up to date and the water quality certificate, according to Decree 33601.
• Maritime-terrestrial zone. If the property lies within the 200-meter coastal strip regulated by Law 6043, it is usually held under a municipal concession, and the first 50 meters from the high tide line are public zone. Confirm where the treatment system actually sits.

For a broader overview, see wastewater permits in Costa Rica.

Red flags

Be cautious if you find any of the following:

• Wet, smelly or very green patches over the drain field, especially in the dry season.
• A tank that has been pumped several times in a short period.
• No plans for the system, or plans that do not match what is on site.
• A plant with no logbook, no operator or missing operational reports.
• A pipe running to a creek or the beach without a discharge permit.
• A health order from the Ministry of Health, or neighbor complaints.
• Drain fields under parking or patios, or septic tanks with no access lid.
• Occupancy or number of rooms well above what the system was designed for.

None of these automatically kills a deal, but each one has a cost that should be reflected in the price or fixed before closing.

Get a second opinion before closing

Ingeniería de las Aguas is a wastewater engineering firm based in Palmares, Alajuela, that designs, builds and redesigns septic systems and treatment plants and handles their permits. We work with properties in Guanacaste and other regions of the country. If you are considering a property, send us its location, the type of system and any documents you have, and we will tell you what to look at.

Message us on WhatsApp or use our contact page. Spanish-speaking readers can also read our guide on buying a house with a septic tank.