Lot Drainage and Where the Water From Your Work Goes

Why this matters

Almost every residential trade makes water that has to go somewhere: a condensate line, a drained pool or spa, a new sump pump's discharge, the runoff from a pressure-washed driveway. The tech chooses where the hose ends, usually in the ten seconds before the water starts, and that choice is the one the city's stormwater inspector, the sewer utility and the neighbor will judge. Put the wrong water in the wrong pipe and the shop is the discharger on record. This card sorts the four kinds of water a shop produces by what they carry, the two public systems that may or may not take them, and where the shop's responsibility actually sits.

Two pipes under the street, and why each one refuses things

Most towns run two separate systems, and the rules follow from what each is built to do.

The sanitary sewer carries wastewater to a treatment plant. It is sized for sewage, and clear water from roofs, foundation drains and sump pumps is the enemy of that sizing: in a heavy rain it fills the pipes, overflows manholes and backs sewage into basements. That inflow is why municipal sewer codes in most places prohibit connecting clear water to the sanitary system, and why the plumbing codes as adopted say the same thing; the IPC's storm drainage chapter, as adopted by your jurisdiction, forbids draining storm water into a sewer intended for sewage only. The plant can usually handle chlorine, soap and modest volumes, which is why some towns send pool water this way.

The storm sewer carries rain from streets and yards straight to a creek, lake or bay, usually with no treatment at all. Whatever goes into a street inlet arrives in the water body as it was. At the federal level, the Clean Water Act's stormwater rule at 40 CFR 122.26 requires the larger municipal storm systems to prohibit non-stormwater discharges into them, and lists a set of discharges a city need address only if it finds them to be a significant source of pollution, among them foundation and footing drains, crawl space pump water, air conditioning condensation, individual residential car washing and dechlorinated swimming pool water. The state permit and the city's own ordinance sit on top of that floor and routinely go further: a city may prohibit any of those listed discharges outright, and a city with a combined sewer, one pipe for both, has rules unlike either.

So the federal layer tells you what a city's storm system may tolerate. Only the city's ordinance tells you what it does, and that is the document to read.

Where each kind of water may go

Condensate. The IMC, as adopted by your jurisdiction, requires condensate to go to an approved place of disposal and not into a street, alley or other area where it causes a nuisance, at 307.2.1 in the 2018 and 2021 editions. An air conditioner's condensate is close to distilled water. A condensing furnace's or water heater's condensate is acidic, often in the pH 3 to 4 range, and some manufacturers, and some jurisdictions, call for a neutralizer before it reaches a drain, especially a cast iron or septic one. Condensate is commonly allowed into the sanitary drainage system through an indirect connection with an air gap or air break, and to the yard in many places. What causes the callback is a line discharging over a walkway that ices in January, or into the foundation backfill where it feeds a wet basement.

Pool and spa water. This is where the rules diverge most. Some towns require pool and spa water to go to the sanitary sewer through the house cleanout at a limited rate, because chlorinated water kills the creek. Others prohibit it from the sanitary system, to protect capacity, and allow it to the storm system or the yard only after it is dechlorinated and its pH brought into a stated range, often with a waiting period after the last chemical dose. Salt-chlorinated pool water adds a third issue, because the salt that damages plants and soil does not leave with the chlorine. A spa's few hundred gallons of bromine-treated water is a small volume with the same questions.

Sump and foundation drain water. Clear groundwater, and the one discharge almost every sewer utility forbids from the sanitary system. It goes to the yard, a dry well or the storm system where the city allows a connection. IRC R405 as adopted covers the foundation drainage itself; the discharge location is set by the city's ordinance and by the lot. The callbacks are a discharge that runs back to the foundation, one that freezes into a sheet across a public sidewalk, and one aimed at the next lot.

Wash water. Pressure washing a driveway, a deck or a house picks up detergent, oil, sediment and paint, including lead paint chips on houses built before 1978. Many cities prohibit wash water from entering the storm drain at all, and some make an exception for plain water with no detergent. The usual compliance methods are blocking the nearest storm inlet with a mat or berm, vacuum recovery of the water, and disposal to a sanitary drain with the sewer utility's permission or onto a vegetated area where the city allows it. Where the surface carries lead paint, the debris is a lead-safe work practices question first, and a sibling card owns it.

The neighbor's lot

Water a shop sends across a property line is governed by private law, not by the plumbing code, and the states differ. Some follow versions of the common enemy rule, in which an owner may generally protect against surface water even if it flows on to a neighbor; others follow the civil law rule, under which an owner may not change natural drainage to a neighbor's harm; many now apply a reasonable use test that weighs both sides. Under every one of them, deliberately aiming a pump hose, a sump outlet or a wash-water stream at the next lot is the fact pattern a neighbor's complaint is built on. This is not legal advice: whether a particular discharge creates liability, and for whom, is a question for the homeowner's attorney and the shop's. The operating rule that keeps a shop out of that question is simple. The water ends on the customer's lot or in a public system that accepts it, never on someone else's land.

Worked example: one pool, two towns

A pool service is draining a 16,000-gallon plaster pool for resurfacing. The pump moves 35 gallons per minute.

Pumping time. 16,000 divided by 35 is about 457 minutes, about 7.6 hours. That number decides whether the job is a one-visit drain or an overnight one, and whether someone must stay with the hose.

In this town, the ordinance requires pool water to go to the sanitary sewer through the house's sewer cleanout, at no more than 40 gallons per minute, with notice to the sewer utility. At 35 gallons per minute the pump sits under the cap, 40 minus 35 leaving 5 gallons per minute of margin, so no throttling is needed. The hose goes into the cleanout and is tied off so it cannot whip out under pressure. No dechlorination is required for the sanitary route.

In the next town, 4 miles away, the ordinance prohibits pool water from the sanitary system and allows it to the storm system only after the chlorine reads below the detection limit of a standard test, the pH is between 6.5 and 8.5, and no chlorine or other sanitizer has been added for 7 days; a dechlorinating chemical is allowed. The pool tested at 2.5 ppm free chlorine on day 0. The service stopped dosing, waited out the 7 days with the pool covered, tested again on day 7 and read 0.4 ppm, still above detection, so the drain did not start; a dechlorinating chemical was dosed to the label rate and the test then read below detection with pH 7.4. Only then did the hose go to the street, and the 7.6 hours of pumping ran into the inlet in front of the house.

The same pool, the same pump and the same 7.6 hours produce opposite instructions 4 miles apart. That is the whole point of reading the local ordinance before the job, and it belongs on the jurisdiction profile.

Two hazards ride on the drain itself. The submersible pump plugs into a GFCI-protected outlet, with the cord routed so it is not in the water path or under a closing gate. And an in-ground pool emptied where the groundwater is high can float or crack: before a full drain, the service checks the hydrostatic relief valve and the local water table, and where groundwater is near the floor it stops the drain and calls the resurfacing contractor and, if needed, an engineer, rather than finishing the drain. See related: High Water Tables and Wet Basement Regions.

What the trade owns

The shop that places the hose and starts the pump is the one producing the discharge in that moment, whatever the homeowner owns. In practice that means four things, each checked before the valve opens:

• The water is identified: what is in it, with a test result where the rule turns on one.
• The destination is a permitted one under the city's ordinance for that water, read from the ordinance or the profile, not from habit.
• The path stays on the customer's lot until it reaches that destination, and does not cross a sidewalk where it will freeze or a property line where it becomes the neighbor's.
• The volume and the rate are known, because a permitted route at a permitted rate can still overflow a cleanout or a swale.

Write the destination and the test results on the ticket. When a stormwater inspector or a neighbor asks, those two lines are the shop's answer.

References

• U.S. EPA, 40 CFR 122.26, the stormwater regulation for municipal separate storm sewer systems, and the state stormwater permit and municipal ordinance built on it.
• International Mechanical Code 307.2.1 and the International Plumbing Code storm drainage chapter, in the edition your jurisdiction adopted; International Residential Code R405 for foundation drainage.
• The city's sewer use ordinance and stormwater ordinance, which set the actual destinations and conditions.
• See related: High Water Tables and Wet Basement Regions; How to Build a Jurisdiction Profile; Property Lines, Easements and Where Equipment Can Go.