Tile Drainage Before You Buy: Why Tile Maps Matter on Central Illinois Farmland
Why Harvest Is the Best Time to See What a Tile System Is Actually Doing
A drainage problem on central Illinois farmland is most visible in two windows: early spring when the ground is saturated and the problem areas are standing in water, and fall at or after harvest when the crop is gone and the soil surface tells the story of what happened during the growing season. The combine yield monitor, if the selling tenant is willing to share the data, is the most precise tool for identifying drainage-limited areas — a field that averages 220 bushels of corn with a wet corner that consistently produces 160 to 170 bushels is showing a yield drag that has a drainage explanation in most cases. A buyer who walks that field in October and sees the color difference in the harvested stubble — darker, more compacted, slower to dry — is seeing the physical evidence of the same drainage limitation the yield monitor recorded.
A tile system that is working well is invisible in October. The field drains, the crop yields uniformly, and there is nothing to see. A tile system with a failed section, a collapsed main line, or a compromised outlet produces evidence that harvest makes visible: wet spots that are still wet in October when the surrounding field has dried down, areas where the combine left more compaction marks than the rest of the field, and field edges or corners where the crop came off shorter and less uniformly than the surrounding acres. These are the areas that a buyer walking a property before making an offer should mark and investigate.
How to Read a Tile Map Before You Bid
A tile map is a drawing — sometimes hand-sketched, sometimes GPS-plotted — that shows the location, depth, size, and direction of the tile lines in a field. The main line is the primary collector that carries drainage water to the outlet. Laterals branch off the main at regular intervals — typically every 40 to 60 feet on high-PI central Illinois soils — and collect water from the surrounding soil. The outlet is where the tile system discharges, either to a drainage ditch, a creek, or a constructed outlet structure.
When reviewing a tile map before an offer, identify the following: where the main line runs relative to the wet spots you observed in the field, whether the lateral spacing is adequate for the soil type, where the outlet is located and whether it has access for maintenance, and whether any sections of the map show gaps or indicate where tile coverage is absent. A tile map that shows coverage on 120 of 160 acres means 40 acres are undrained — the question is whether those 40 acres are the upland areas where natural drainage is adequate, or whether they include field areas that should be tiled but are not.
A GPS tile map is more reliable than a hand-drawn map because it was plotted from actual measured positions rather than from memory or estimation. When a seller provides a hand-drawn map, ask whether the tile was installed by the current owner (who can confirm its location from memory) or was inherited from a prior owner (in which case the map's accuracy may be uncertain). A tile system installed 40 years ago on a hand-drawn map that has changed hands twice since installation is a tile system whose actual location should be verified by camera inspection or by a tile contractor who can locate the lines with a signal finder before the buyer relies on the map for a purchase decision.
Spotting a Failing Line in the Field
A failing tile line produces specific symptoms in the field that a buyer can observe at harvest. The most obvious is a linear wet stripe running perpendicular to the direction of tile flow — a section of the field that stays wet while the surrounding acres dry, following the path of a collapsed or blocked lateral. If the wet area is linear and runs in a direction that is consistent with the lateral spacing shown on the tile map, the wet area is almost certainly a tile problem and not simply a soil type variation.
A failing outlet or main line produces a different pattern: a broader wet area that includes multiple lateral zones, because the water that the laterals are collecting cannot get to the outlet efficiently. If the main line is compromised, the symptom is not a single wet stripe but a zone of poor performance that gets worse in the direction of the outlet. A field where the performance degrades progressively toward the drainage outlet is showing a main line or outlet problem rather than an isolated lateral failure.
Ask the selling tenant, if accessible, whether they have observed specific problem areas in the field over multiple years. A tenant who has farmed the ground for 10 years knows exactly where the drainage problems are, when they appear during the growing season, and what years they were most pronounced. That information is available through a direct conversation and is more reliable than anything a buyer can observe in a single October walk.
How to Price Drainage Repair Into a Fall Offer
A drainage repair estimate from a licensed Illinois drainage contractor provides the buyer with the information needed to negotiate a price adjustment. Get an estimate before making an offer, not after. A buyer who makes an offer contingent on a satisfactory drainage inspection is in a weaker negotiating position than a buyer who has already obtained a contractor estimate, knows the repair cost, and has submitted an offer that reflects that cost in the purchase price.
The repair cost variables that determine what to price in are: whether the problem is a single failed lateral (typically $2,000 to $5,000 to locate and repair), a main line section failure (typically $5,000 to $15,000 depending on depth, material, and access), or an outlet situation that requires a new structure and regrading (which can reach $20,000 to $50,000 on ground with outlet access challenges). The cost of a full GPS tile map and camera inspection on a farm with undocumented drainage is typically $1,500 to $4,000 — money that either identifies a problem the buyer can price into the offer or confirms the system is in good condition, which supports the asking price.
A buyer who submits an offer on farmland with an identified drainage problem and no price adjustment for that problem has left money in the negotiation. A buyer who submits a market-rate offer alongside a contractor drainage repair estimate, referencing the estimate as the basis for a purchase price that is $X below the asking price, is making a transparent, documented offer that a seller and their broker can evaluate against the alternative of fixing the drainage themselves before relisting. In a market where sellers want to close before year-end, that conversation is often more productive than the seller's initial response suggests.
Jared Williams is the Managing Broker and owner of Archer Realty & Auction LLC. He is a licensed Illinois auctioneer and serves on the Menard County Board of Review, specializing in farmland valuation, auction, and sale across central Illinois. Start the conversation at archerrealty.net.
