Buying a home with a wastewater treatment plant in Costa Rica: due diligence checklist

A condo in a gated community near the beach, a villa in a resort development, a small hotel in the hills: in many parts of Costa Rica there is no public sewer, so the property's wastewater goes to a treatment plant shared by the whole development. When you buy in, you buy a share of that plant too, along with its permits, its monthly costs and any problems it already has.

This guide is a checklist for buyers of properties served by a treatment plant. If you are buying a house with its own septic tank, see our guide on buying property with a septic system instead. For an overview of the permits involved, see wastewater permits in Costa Rica. The information here is general and based on the regulations in force in November 2026; it does not replace a review of the specific property.

First, a few terms

• Condominium administration / HOA. Costa Rican condominiums are run by an assembly of owners and an administrator. Foreign owners often call this the HOA. In most developments the plant sits on common property, so all owners share its cost and responsibility.
• Ente generador. The legal term for whoever generates the wastewater and answers for it before the Ministry of Health: the condominium, the hotel company, the developer.
• Operational report (reporte operacional). The periodic report that proves the plant meets the legal limits.
• SIRROAR. The Ministry of Health's online system where operational reports are generated.
• Technical responsible (responsable técnico). The professional or certified technician, registered with the Ministry of Health, who prepares and signs the reports.

Checklist part 1: permits and documents

Ask the seller, the developer or the administration for copies of:

1. Approved plans and the location permit. Under Decree 39887-S-MINAE, a treatment system needs a location permit from the Ministry of Health before its plans are reviewed, and then approved construction plans. Check that the plant on the ground matches the approved plans.
2. Discharge permit, if the plant discharges to a river, creek, estuary or the sea. It is issued by MINAE's Water Directorate (Dirección de Agua). Plants that infiltrate into the ground or reuse the water for irrigation follow other rules; ask which route this plant uses and for the documents of that route.
3. Health operating permit (permiso sanitario de funcionamiento), when the activity needs one, such as a hotel. Under the Wastewater Discharge and Reuse Regulation, this permit cannot be renewed without operational reports up to date and the Ministry's annual water-quality certification.
4. The operation and maintenance manual prepared with the design.
5. SETENA environmental approval, if the development went through it. SETENA is the National Environmental Technical Secretariat; larger developments usually have a file with environmental commitments that may involve the plant.

If nobody can find the approved plans or the location permit, that is your first red flag.

Checklist part 2: is the plant actually working?

Paper permits only tell you the plant was approved. These documents tell you whether it works:

1. Operational reports for at least the last two years. Decree 33601-MINAE-S sets the schedule (article 46): every six months for an average flow up to 100 cubic meters a day, every three months above that, monthly for plants serving several generators. Reports are due within ten business days after each period, and a new plant has three months from start-up to file its first one. Check that none are missing.
2. Lab results inside those reports. Look at the universal parameters: flow, BOD, COD, pH, fats and oils, settleable solids, suspended solids, detergents (MBAS) and temperature. Lab analyses are required every six months for flows up to 100 m³/day and quarterly above that (articles 34 and 35). A pattern of results just over the limit is as important as a single failure.
3. The logbook (bitácora). Article 41 requires a numbered logbook recording daily operation, maintenance, results, incidents and where the sludge went. A thin or blank logbook usually means a plant nobody really operates.
4. The technical responsible. Ask who signs the reports and confirm they are registered with the Ministry of Health. Registration lasts two years.
5. Sludge records. Plants produce sludge that has to be removed and disposed of legally. Ask how often it is removed, by whom and where it goes.
6. Health orders. Ask in writing whether the Ministry of Health has issued any health order (orden sanitaria) about the plant, and whether it was resolved. Pending orders come with deadlines that the new owners inherit.

Checklist part 3: capacity and the future

A plant designed for the first phase of a development may not cope with the finished project.

• Design flow vs reality. Compare the design flow in the plans with the number of units built, planned and occupied. Decree 39887 asks for designs covering at least five years, including growth.
• Phases. If more units are coming, ask whether the plant was designed to be expanded in stages and who pays for the expansion.
• Rental use. Short-term rentals at full occupancy produce more wastewater than the same units used as second homes. Ask whether high-season flows were taken into account.
• Changes need approval. Any change to the design of a plant must be authorized by the Ministry of Health before work starts, so "we will just add a tank" is not a quick fix.

Checklist part 4: the budget

The plant is a permanent line in the condo budget. Ask to see it, and check that it covers:

• operation staff or an operation contract, which Decree 39887 requires at all times (article 29);
• electricity, especially for aerated plants, where blowers run around the clock;
• lab analyses and the technical responsible's fees for the reports;
• sludge removal;
• the environmental discharge fee (canon) under Decree 42128-MINAE-S, paid quarterly by plants that discharge to a water body;
• a reserve for pumps, blowers and repairs.

A budget with no line for the plant, or a very small one, often means maintenance is being postponed. Sooner or later that turns into a special assessment.

Questions to ask the administration

• Who operates the plant day to day, and under what contract?
• When was the last operational report filed, and did it comply?
• Have there been odors, overflows or neighbor complaints in the last two years?
• Has the Ministry of Health inspected the plant or issued any order?
• Is any upgrade, expansion or redesign planned or under discussion?
• Who keeps the logbook, the manual and the permits, and can I see them?

Red flags

• No approved plans or location permit available.
• Missing operational reports, or results that fail repeatedly.
• A logbook that is empty or written all at once.
• Plant equipment switched off, bypass pipes or discharges to a ditch.
• Strong odors, foam or dark water at the outlet.
• A plant clearly smaller than the development it serves.
• No budget line for operation.

None of these automatically kills a deal, but each one has a cost, and it is better to know it before you agree on a price.

What an engineering review includes

For a significant purchase, a review by a wastewater engineer usually covers: a site visit to the plant and the discharge or infiltration point; comparison of the built plant with the approved design; review of permits, the logbook and recent operational reports; a capacity check against current and future units; a list of corrections with their priority; and an estimate of operating costs. The result helps you negotiate or plan, and it gives the condominium a clear starting point if work is needed.

How we can help

At Ingeniería de las Aguas we design, build, upgrade and rehabilitate treatment plants, prepare operational analyses and follow up on existing systems, and we manage permits with the Ministry of Health, MINAE and other agencies. Our page on HOA wastewater plant compliance explains how we support condominiums after the purchase. If you are about to buy, send us the location, the number of units and whatever documents the seller has shared on WhatsApp, or contact us through our contact page. We will tell you what to look at first.