The terms that show up on quotes, in conversations with estimators, and in marketing copy — defined without jargon. PSI vs GPM, soft wash vs pressure wash, surface cleaner vs wand, sodium hypochlorite vs detergent, ARMA-compliant roof cleaning, capture-mat protocol, oxalic pre-treatment, and more. Useful before you book or while comparing quotes from different contractors.
Core technique terms — pressure vs soft, PSI vs GPM
Four terms that decide what your quote actually means
Pressure washing — uses mechanical force from high-PSI water (1,500-4,000 PSI) to physically blast contamination off the surface. Best for hard surfaces (concrete, brick, paving stones) that can take the impact. Soft washing — uses chemistry (sodium hypochlorite plus surfactant) at low pressure (under 500 PSI) to dissolve contamination, then water rinses it away. Best for siding, roofing, painted wood, stucco — anywhere mechanical force would damage the substrate. Calgary residential work is roughly 70% soft wash, 30% pressure wash by job count.
PSI (pounds per square inch) — measures water pressure at the nozzle. Soft-wash range under 500 PSI. Mid-pressure 1,500-2,500 PSI for vinyl siding rinse and gentle concrete. High-pressure 2,500-4,000 PSI for heavily contaminated flatwork. PSI breaks the bond between contamination and surface; too much PSI damages the substrate.
GPM (gallons per minute) — measures water flow volume. Higher GPM flushes contamination away faster even at the same PSI. Residential units run 2-4 GPM; commercial 4-8 GPM. Hartford uses commercial-grade 4-5.5 GPM units on residential work — speed without the PSI risk. A quote that doesn't mention either PSI or GPM is a quote that should be questioned. Pair this with pressure washing and soft washing service detail pages.
Recent work
Chemistry vocabulary — what's actually in the bottle
Four chemistry terms that show up on every quote
Sodium hypochlorite
The primary soft-wash active. Same compound used in municipal water treatment and household bleach. Breaks down to salt water within hours of contact. Standard residential dilution: 1-3% active.
Surfactant
Soap-like additive that helps chemistry stick to vertical surfaces long enough to work. Biodegradable formulations are the modern standard (OECD 301B certified).
Oxalic acid pre-treatment
Mild acidic cleaner used to dissolve calcium, magnesium and rust mineral deposits. Always paired with alkaline neutralisation rinse to prevent acidic residue on substrate.
Neutralisation rinse
Final fresh-water rinse after acidic chemistry use, bringing the substrate pH back to neutral. Prevents premature substrate wear and protects landscaping below.
Equipment and protocol terms — what's on the truck and how the work runs
Four operational terms that affect speed, results and environmental footprint
Surface cleaner — 16-21-inch disc with two rotating nozzles inside a closed housing. Concentrates water on the cleaning area, eliminates overspray, produces uniform cleaning with no streak lines. 4-6x faster than open wand on flatwork. Hartford uses 21-inch surface cleaners on all residential driveways.
Open wand — single-point spray with a trigger gun. Efficient for vertical walls, foundations, edges, detail work. Slow and streak-prone on flatwork — should not be the primary tool for driveway cleaning.
Capture-mat protocol — absorbent mats deployed at ground level to collect rinse water before it reaches storm sewer or natural waterway. Standard on Chestermere lakefront work and chemistry-heavy jobs. Optional eco-upgrade on inland properties (+15-20% per service).
ARMA-compliant — Asphalt Roofing Manufacturers Association standard for roof cleaning. No walking on shingles, no pressure washing, only low-pressure soft-wash chemistry from ladder or extension wand. Preserves manufacturer warranty; non-compliant cleaning can void warranty. Hartford's roof cleaning is ARMA-compliant by default.
More terms worth knowing: pure-water-fed pole (zero-chemistry window cleaning), no-walk method (roof cleaning from ladder/extension only), efflorescence (white mineral bloom on brick and concrete that needs specific chemistry), saponification (oil-stain breakdown using alkaline chemistry). Pair this page with environmental commitment and roof cleaning for the deeper technique detail.
40+Terms covered
30+Service pages linked
10 minReading time
Term-by-service — where each glossary term applies
Six service pages where the glossary terms get used
Each service page applies a specific subset of the glossary; click through to see the term in context.
Five questions about the most-asked glossary terms in plain language.
Pressure washing uses mechanical force — high-PSI water (1,500-4,000 PSI typical) sprayed through a nozzle that physically blasts contamination off the surface. Best for hard surfaces (concrete, brick, paving stones) that can take the impact. Soft washing uses chemistry — sodium hypochlorite plus surfactant applied at low pressure (under 500 PSI), with chemistry doing the actual cleaning work, water doing the rinse. Best for siding, roofing, stucco, painted surfaces, anywhere mechanical force would damage the substrate. Hartford uses both depending on what the surface needs.
PSI (pounds per square inch) measures water pressure at the nozzle. Soft-wash range: under 500 PSI for siding, roofing, painted wood, stucco — anything that pressure could damage. Mid-pressure range: 1,500-2,500 PSI for vinyl siding rinse, gentle concrete cleaning, deck surfaces. High-pressure range: 2,500-4,000 PSI for heavily contaminated concrete, brick, paving stones, commercial pad cleaning. Calgary residential work mostly lives in soft-wash and mid-pressure ranges; high-pressure is reserved for flatwork.
GPM (gallons per minute) measures water flow volume at the nozzle. Higher GPM = more water moving across the surface per minute = faster cleaning even at the same PSI. Residential pressure washers typically run 2-4 GPM; commercial units run 4-8 GPM. Why it matters: PSI breaks the bond between contamination and surface, GPM flushes the contamination away. Equal PSI with double the GPM gets the job done in half the time. Hartford uses commercial-grade 4-5.5 GPM units on residential work for speed without the PSI risk.
A surface cleaner is a 16-21-inch disc that rolls across flat surfaces with two rotating spray nozzles inside a closed housing. The closed housing concentrates water flow on the cleaning area (no overspray waste), produces uniform cleaning with no streak lines, and works 4-6x faster than an open wand on flatwork. Open wand is single-point — efficient for vertical walls and detail work, slow and streak-prone on driveways. Hartford uses 21-inch surface cleaners on every residential driveway; the wand handles wall sections, foundations, edges and detail.
ARMA is the Asphalt Roofing Manufacturers Association — the industry body that publishes shingle cleaning standards. ARMA-compliant means: no walking on the shingles (foot traffic damages the granule layer that protects the asphalt), no pressure washing (high PSI strips granules), only low-pressure soft-wash chemistry application from a ladder or extension wand. Roof cleaning that meets the ARMA standard preserves your manufacturer warranty; cleaning that violates it can void the warranty if the manufacturer detects damage. Hartford's roof cleaning is ARMA-compliant by default.
Calgary clients who used the glossary
What clients say about understanding the work
★★★★★4.9· 75 reviews on Google
★★★★★
Read the glossary before my quote walk. When the estimator mentioned PSI ranges and ARMA-compliant roof cleaning, I knew what they meant. Made the conversation about scope instead of jargon translation.
Homeowner
Calgary · Tuscany
★★★★★
Compared three pressure washing quotes. Two didn't mention PSI or GPM. Hartford did. Picked Hartford. The glossary made it obvious which contractor knew what they were talking about.
Homeowner
Calgary · Mission
★★★★★
ARMA-compliant roof cleaning was the deciding factor — my shingles are only 4 years into a 25-year warranty. Hartford was the only quote that brought it up.
Homeowner
Cochrane · RancheView
★★★★★
Liked the plain language. Most contractor sites read like sales brochures. This one reads like someone explaining the work to a curious neighbour.
Homeowner
Calgary · Inglewood
Term you didn't see covered?
Ask about any pressure washing term at the quote stage
The estimator explains every term that comes up on the written quote — PSI ranges for your specific surfaces, GPM rating of the equipment, chemistry choices, whether captured-rinse applies to your property. No jargon, no mystique — straight answers.
