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This technique is preferred because the nozzle
is designed with a reverse flow head configuration that literally
"pulls" the hose away from the powerwasher operator
and towards the sources while flushing biomass and debris down
the line and on to the collection point. Another benefit to washing
in a reverse flow direction is that most plumbing fittings have
smooth swings in the reverse direction and this seems to help
reduce the number of obstruction interferences. Though this is
the preferred method, trial and error may have to be applied due
to the complexities of the piping infrastructure. For immediate
success, select straight sections that are observed to contain
biomass. In other locations, piping may have to be removed or
modified in order to reach areas of concern. Powerwashing on
thermo-plastic piping will require a lot more trail and error
and it may be necessary to remove piping sections to verify cleaning
effectiveness. Note thqat the installation of a sight glass may
help to minimize the amount of sections to be removed. Sometimes
it will be difficult or impossible to feed the hose and nozzle
in reverse direction. In these cases, an alternative method would
be to to start at the sources (sink traps or floor drains) and
work in the direction of flow. This technique, however, is less
desirable because the nozzle head will not be flushing debris
as it moves along the piping. It may be necessary, in this instance,
to apply additional water to aid the flushing process by turning
on an adjacent sink that is tied into the same conveyance line.
The following are some precautions that should be considered prior
to implementing powerwashing procedures: 1) It should be assumed
that all materials contained within the conveyance piping are
hazardous, and, prior to beginning powerwashing activities, approval
by the institution's Health and Safety Officer should be obtained
to help ensure that proper personnel protective equipment is being
used; 2) Powerwashing is not a delicate operation and sometimes
conveyance fittings and piping, especially with glass fittings,
can be cracked or broken. It is necessary to inspect the entire
run prior to powerwashing, and identify any potential obstructions,
so that if a fitting is broken, a replacement fitting is immediately
available for instillation; and, 3) Conveyance piping that contains
large amounts of biomass may, once dislodged, begin to collect
and clog downstream conveyance piping sections. If the piping
begins to clog and eventually prevents flow due to accumulation
of this dislodged biomass, there will be a significant potential
for wastewater backing up in the plumbing system and causing flooding
at lower elevation locations.
All powerwashing wastewater that contains removed biomass should
be assumed to contain levels of mercury above the MWRA's allowable
discharge limit of one (1) ppb, and should be collected for off-site
disposal. Refer to Section 10.0 for recommended mercury waste
disposal procedures.
The collection of the powerwash wastewater will be a difficult
task but, since powerwashing will usually occur during non-operating
hours, the systems, hopefully, will be virtually drained. Once
flow has stopped, the treatment tank can then be emptied and used
as a powerwashing wastewater collection vessel. After powerwashing
is completed or the treatment tanks are getting full, transfer
all collected wastewater into storage containers. This is only
one recommended method for collecting wastewater and, there are
other collection and pumping methods that can be used on a case-by-case
basis. However accomplished, it is very important that this wastewater
is collected and not be allowed to be discharged.
A typical piece of equipment that has been used by Beth Israel
Hospital in the power washing of their infrastructure piping is
the KJ-1250 Water Jetter (See Appendix C). This unit is a compact,
portable machine designed to clear biomass, grease and sludges
out of 1-1/4" to 4" diameter drain lines. It can be
either hand carried or combined with a two wheel cart and hose
reel for easy transport.
The equipment specifications are as follows:
|
Line capacity
|
1-1/4" to 4" drain lines through 150
feet
|
|
Motor
|
115V/60 Hz TEFC or 240 V/50Hz
|
|
Rating
|
11/2 Hp @ 1725 RPM
|
|
Pump>
|
Duplex Plunger
|
|
Pressure
|
1500 PSI
|
|
Flow Rate
|
1.5 GPM
|
|
Weight
|
70 lbs
|
The powerwasher mentioned in this section does not allow for the
addition of chemistry as powerwashing is performed. This limitation
is do to the long lengths of hose and the design of the equipment.
A powerwasher with the capabilities of adding chemicals and high
pressure water simultaneously could further enhance the effectiveness
of the washing. Further investigation of other powerwashing equipment
that aspirate chemical during powerwashing are currently available
or facilities should work with vendors of existing equipment to
see if their units could be modified to incorporate this feature.
The basic unit can be used with water only to provide a scouring
agitation. However, it is recommended that a bleach solution
be added to the length of piping at the source, if possible, to
help disinfect that section prior to powerwashing. Before adding
bleach or an other disinfectant chemical, it should all be analyzed
to ensure that it is mercury free or of a "low" mercury
content. The MWRA/MASCO Hospital Work Group, Operations Subcommittee
has identified that several chemicals and reagents, including
many disinfecting products that contain bleach, also contain
considerable amounts of mercury
The addition of surfactants, dispersants, caustics and/or wetting
agents could potentially increase the powerwashing effectiveness.
To date, there have been eight cleaning chemicals and combinations
of these chemicals investigated through a pipe cleaning protocol
effort that was developed for Medical Academic and Scientific
Community Organization, Inc. (MASCO). The results of this protocol
are presented in Section 8.0 of this Guidebook.
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TABLE OF CONTENTS
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