Pool drainage: keeping water away from your pool and house

Because we get a lot of water and our ground does not take it in quickly. National Weather Service normals for Akron-Canton, the 1991 to 2020 averages, add up to roughly 41 to 42 inches of precipitation a year, with May, June and July each averaging more than 4 inches. Much of the region sits on glacial till soils that drain slowly. The USDA rates Mahoning silt loam, one of the most widespread, as somewhat poorly drained with a perched water table 6 to 12 inches down from October through June in most years.

Put those together and a heavy summer storm sends water across the surface rather than into the ground. A pool and deck change the way a backyard sheds that water. Concrete does not absorb anything, the pool sits in a hole, and the equipment pad is usually tucked beside the house. Without a plan, water collects where you least want it: against the pool, under the deck or along the foundation.

The Residential Code of Ohio, Section 401.3, requires surface drainage to be diverted to a storm sewer or another approved point of collection that does not create a hazard, and it requires lots to be graded so water drains away from foundation walls. The ground must fall at least 6 inches within the first 10 ft. Where lot lines, walls or slopes make that impossible, drains or swales have to carry the water away instead, and paved surfaces within 10 ft of the foundation must slope at least 2 percent away from the house.

A pool deck that runs up to the back of the house is one of those paved surfaces. It has to pitch away from the house, and if it also has to pitch away from the pool, the two slopes meet somewhere in the middle. That low line needs a drain, or water will sit there and freeze every winter.

Away from the pool, and away from the house. Water that runs toward the pool carries grass clippings, fertilizer and dirt into the water and can seep down along the coping into the backfill. Water that runs toward the house ends up in the basement.

Even for private pools, the idea mirrors the rule Ohio applies to public pools: the Ohio Building Code says decks around a public pool are to be built to prevent any standing water and are not permitted to drain into the pool. It is good practice for a backyard pool too. On a simple rectangle of concrete, the deck pitches outward on all sides to the lawn. On a bigger patio, or one that meets the house, we set a low line and catch it with an area drain or a trench drain.

Catch it before it arrives. In most yards that means a swale, a shallow, grassed channel shaped into the lawn uphill of the pool that collects surface water and carries it around the pool to a lower point. On steeper or tighter lots, a row of area drains or a trench drain at the edge of the upper patio does the same job and pipes the water away.

Where the water goes matters as much as catching it. The discharge point should be somewhere the water can go without flooding a neighbor or a lower part of your own yard: a storm sewer connection where the town allows it, a ditch, a lower part of the lot that can take it, or a dry well where the soil can absorb water. In clay, dry wells have limits, because the ground around them fills up quickly in a wet spring. We check the town's rules and the soil before choosing.

Neighbors matter here too. Changing grades in your backyard can change where water leaves your lot, and pushing more of it onto the house next door creates a dispute nobody wants. A good plan keeps the water leaving your property roughly where it always did, or sends it to a proper drain.

These are two of the most common drainage mistakes around pools. A downspout that used to dump onto the lawn now dumps onto the new pool deck, which sends roof water across the concrete, toward the pool or under the slab. A basement sump pump that discharged into the backyard now empties into the deck area.

Before the deck is poured, every downspout and sump outlet near the pool should be piped underground to a discharge point away from the pool. It is inexpensive while the ground is open and costly after the concrete is down. Solid pipe, not perforated, is the right choice for carrying roof water past the pool area, so it does not leak back into the backfill.

A pool sends water out of the system more often than people expect. Filter backwashing, lowering the water for a winter closing, and draining off heavy rain all send water somewhere. Some towns regulate this. Stow's zoning code, for example, requires a pool to be drained into a municipal storm sewer or another drain approved by the City Engineer, through tightly sealed pipe or hose, and bars draining a pool onto an adjoining property.

Plan a place for this water at the design stage: a discharge line from the equipment pad to the same drainage system the deck uses, or to a spot on your lot that can take it. Let chlorine levels drop before sending large amounts of pool water to a ditch or stream. The DE filter in our packages is backwashed or cleaned on a schedule, and knowing where that water goes saves arguments with neighbors.

On high, solid ground. The pump, filter, heater and electrical controls do not belong in the low corner of the yard where water gathers every spring, or right under a roof edge without a gutter. Set the pad slightly above the surrounding grade, on a firm base, with the ground sloping away from it on every side.

Keep the pad clear of downspout discharge and away from the path of any swale. A heater sitting in standing water rusts from the bottom, and a pump motor that floods fails. It also helps to leave room around the pad for service, so nobody has to stand in mud to open the filter.

Winter adds its own drainage problem. Snow shoveled or blown off the patio tends to end up in a pile beside the deck, and in March that pile melts into the same spot every day and freezes again every night. In the snowbelt counties, with lake-effect snow, the piles get large. Pick a snow storage spot downhill of the pool and away from the house, and do not pile snow on the pool cover or against the fence.

The deck slope that sheds summer rain also sheds meltwater, as long as the drains and swales are kept clear of leaves in the fall. A clogged area drain in late winter is how ice sheets form on pool decks.

In Northeast Ohio, the problems usually show up in the first two winters:

• Sections of deck heave or settle as wet soil under them freezes and thaws.
• Ice sheets form across low spots on the deck.
• Dirt and mulch wash into the pool after every storm.
• Water collects around the pool and raises the groundwater against the shell, which becomes a real risk if the pool is ever lowered.
• The basement starts leaking where it never did before, because the new patio pushed water toward the foundation.

Each of these is harder to fix after the fact than to prevent. Tearing out and repouring concrete to change its pitch is expensive. Adding a swale or a drain line before the lawn is restored costs a fraction of that.

Drainage planning is on our list of what every pool build includes, alongside excavation, grading and the concrete deck. On the site visit we look at where water comes from and where it goes now: roof lines, downspouts, the sump outlet, low spots, the slope of the lot and the neighbors' yards. The 3D design then sets the pool and deck elevations so water moves away from both the pool and the house, and shows any swales, drains and pipe runs.

Our fiberglass packages start at $68,400 installed with a 4 ft concrete wrap deck. Extra decking and drainage systems are priced for your yard, because a flat, well-drained lot needs very little and a wet, sloped one needs more. We also build retaining walls and drainage correction as stand-alone work, starting from about $15,000 for outdoor living projects, if your yard needs attention before or without a pool.