Skip to main content

Historic Preservation - Technical Procedures

Spectitle:

Guidelines For Using High Pressure Cleaning Equipment On Masonry

Procedure code:

0451004S

Source:

Prosoco, Inc. Product Literature - Kansas City, Ks

Division:

Masonry

Section:

Masonry Cleaning

Last Modified:

02/24/2012

Details:

Guidelines For Using High Pressure Cleaning Equipment On Masonry



GUIDELINES FOR USING HIGH PRESSURE CLEANING EQUIPMENT ON MASONRY


When used properly, high pressure cleaning equipment can safely and
effectively remove dirt from masonry materials.  However, when NOT
used properly, this type of cleaning equipment can cause severe
damage.

CAUTION:  HIGH PRESSURE CLEANING IS NOT RECOMMENDED FOR USE ON
POROUS SURFACES SUCH AS MASONRY.  RATHER, POROUS SURFACES SHOULD
BE CLEANED USING LOW PRESSURE TECHNIQUES.

There are three important factors to consider when specifying the
use of high pressure cleaning equipment.  All three factors
influence the "impact" of the spray on the masonry surface.  They
are:

    1.   Pressure rating of water from the nozzle in pounds per
         square inch (psi)

    2.   Flow rate of water from the pump in gallons per minute
         (gpm)

    3.   Size and type of nozzle or spray tip


PRESSURE RATING

1.   The pressure rating is the rate of intensity that water is
    supplied to the pump and is measured in pounds per square inch
    (psi).

2.   The pumps most preferred by cleaning contractors are those
    providing adjustable pressure between 500 and 2,000 psi.

3.   Pressures between 1,000 and 2,000 psi are typically used for
    surface preparation cleaning.

4.   For typical masonry cleaning, the pressure rating can range
    from 500 to 1,000 psi.  FOR OLDER AND DELICATE SURFACES,
    HOWEVER, MUCH LOWER PRESSURES MUST BE USED.

    a.   A low-pressure wash generally measures between 100 psi
         and 400 psi.

    b.   A medium-pressure wash generally measures between 400 psi
         and 800 psi.

    c.   A high-pressure wash generally measures between 800 psi
         and 1200 psi.


FLOW RATE

1.   Flow rate is the volume of water supplied by the pump and is
    measured in gallons per minute (gpm).

2.   Higher volume pumps are preferable for masonry cleaning.  They
    allow flexibility in adjusting the water pressure as necessary
    while providing a strong enough flow of water to thoroughly
    rinse dirt and cleaner residue from the masonry.


NOZZLE TYPE AND SIZE

1.   A fan type nozzle providing a 15-40 degree fan is preferred.

2.   Laser tips, O-tips, or any fan spray narrower than 15 degrees
    should NOT be used on masonry.  These types of tips generate
    a concentrated stream of water which can be damaging to the
    surface.

3.   Nozzles should be held perpendicular to the surface at a
    distance between 18 and 30 inches from the surface.


HIGH PRESSURES SHOULD NOT BE USED FOR APPLYING CLEANING COMPOUNDS
TO MASONRY

1.   Complete rinsing and removal of cleaning compounds from
    masonry is difficult when they are applied under pressure.
    Therefore, low pressure spray equipment (50 psi maximum)
    should be used.

2.   Traces of cleaning compounds left in the masonry surface can
    result in severe remedial problems and staining, such as
    efflorescence, vanadium staining, acid burn, rust and other
    metallic oxidation stains.


PRESSURE WASHING WITH HOT WATER

1.   Useful for cleaning when outside temperatures are too cold to
    clean with cold water.

2.   Water temperatures should not exceed 160 degrees.  Higher
    temperatures may adversely react with some chemical cleaners,
    resulting in surface discolorations or streaking.

3.   Hot water is most effective when used in conjunction with
    alkaline cleaning compounds.  It is best used in applications
    for removing paint, grease and oil.

4.   Hot water is NOT effective when used in conjunction with
    acidic masonry cleaners.

                         END OF SECTION