Can I pressure wash my Ottawa pool deck without the runoff contaminating the pool water?

Yes, you can pressure wash your pool deck without contaminating the pool water, but you need to take a few deliberate steps to keep the runoff out of the pool. The key is lowering the water level slightly and directing the spray away from the pool edge before you start.

Before you begin, lower your pool water level by about 15 to 20 centimetres below the normal operating level. This creates a buffer zone so that dirty runoff — which will contain algae, mould spores, cleaning agents, debris, and whatever grime has accumulated on your deck surface — cannot easily splash or flow back into the pool. Even a modest amount of that contaminated water entering the pool can throw off your water chemistry and introduce organic matter that feeds algae growth.

Pay close attention to your spray angle and direction. Always work with the nozzle angled away from the pool, pushing water toward your lawn, garden bed, or a drain rather than toward the pool edge. A 25-degree or 40-degree nozzle tip is usually appropriate for concrete or paver decks — avoid the zero-degree (red) tip, which is aggressive enough to etch concrete surfaces and can actually damage the deck material itself. Keep the wand moving steadily rather than holding it in one spot.

If you plan to use any cleaning solutions — degreasers, deck brighteners, or mould and mildew treatments — be especially careful. Many deck cleaning products contain surfactants, bleach compounds, or phosphates that will disrupt your pool's water chemistry and can cause foam, pH swings, or algae-feeding nutrient spikes if they get into the water. Rinse the deck thoroughly with plain water before allowing any runoff to get near the pool, and consider plugging your skimmer temporarily with a skimmer cover plate or foam plug while you work.

Once you are finished, top the pool back up to normal operating level and test your water chemistry before swimming. Check pH, alkalinity, and chlorine levels — even with precautions, a small amount of runoff may have found its way in, and catching any imbalance early is much easier than dealing with a full-blown chemistry problem later. In Ottawa's warm, humid July and August conditions, algae can establish itself surprisingly quickly when water chemistry slips.

One Ottawa-specific consideration: if your deck has significant winter frost damage — cracking, spalling, or heaved sections — pressure washing can accelerate that deterioration by forcing water deeper into existing cracks. If your deck is showing signs of freeze-thaw wear, it may be worth having a contractor assess it before you blast it with high-pressure water. That kind of deck repair is worth addressing before another Ottawa winter makes it worse.