Vacuum Plumbing Systems:
The Next Frontier in Water Savings
In the world of plumbing design, vacuum
is the next frontier. High performance,
water-conserving systems like a vacuum
plumbing system can be a significant part
of a permanent water saving program. A
vacuum plumbing system, also referred to as
a vacuum drainage system, utilizes a vacuum
toilet with a flush rate of 0.5 gpf. Additionally,
the vacuum plumbing drainage can include
sinks, showers and washbasins.
The most significant installations of vacuum
plumbing systems are in jails and prisons.
California, for example, has mandated that
the design, construction and operation of
all state-owned facilities be certified under
LEED. For projects requiring LEED certification,
several credits may be obtained by
using vacuum plumbing systems due to the
reduced flush rates.
The conventional, low-flow, gravity drain
toilet is 1.6 gallons per flush. A toilet in a
prison cell is used and abused in multiple
ways. A single inmate may flush his or her
toilet as many as 25 flushes in a day. Many
correctional institutional designers use 9,600
gallons per inmate per year as a measure in
calculating total outflow from a facility.
Each vacuum toilet has an electronic flush
valve control system allowing the prison
staff to remotely monitor and control the
quantity of flushes per cell in the facility.
Conventional flush valves have no such
control capability, and the ultimate water
consumption is dictated by the facility
A design study done at one correctional
facility with 1,650 toilets using the conventional
1.6 gpf rate showed a water savings
of 19.5 million gallons of water per year
if the facility had been designed with a
vacuum plumbing system incorporating a
Construction Cost Savings
Offered as an alternative to conventional
gravity drainage plumbing, the design of
a vacuum plumbing system is no longer
limited by the rules of a gravity drain system.
The vacuum plumbing system drainage
can be lifted up and easily conveyed to
avoid restrictive site or structural issues.
Piping can be routed vertically and horizontally
and still maintain the necessary
pipe velocity, virtually reducing to zero the
chance of drain line blockage.
The conventional 1.6 gallon-per-flush
toilets have led to some unexpected problems
in older gravity piping. In some installations,
the conventional low flow toilet
flush has been insufficient to carry all of the
sewage from the point of use to the sanitary
drain resulting in drain line blockage
in both the horizontal and vertical legs of
Depending on code, vacuum waste piping
materials can be pressure rated schedule
40 PVC, CPVC, Type M or better copper
or stainless steel; all with DWV pattern
The vacuum waste piping is smaller in
diameter than gravity drain piping. The way
the vacuum drainage system functions is
that air becomes the transporting medium
for the gas and/or the suspended solids.
The negative pressure provides the energy
and by using smaller pipe sizes an optimum
transporting velocity is attained.
By Bruce R. Blanchart, Yardley Pump and Vacuum, Inc.
Continued on page 30