Federal Aviation

MMEL Policy Letter (PL) 83, Revision 8 GC


May 11, 2015


All Aircraft Evaluation Group Managers


Manager, Air Transportation Division, AFS-200

Reply To Attn Of:

Manager, New Program Implementation and International Support Branch, AFS-240


This GC is an approved addendum to all existing MMEL documents. The operator may seek use of the specific relief contained in the PL by revising the Minimum Equipment List (MEL). In doing so, the sample proviso stating the relief in the PL must be copied verbatim in the operator's MEL. Approval of the revised MEL is gained utilizing established procedure, through the assigned Principal Operations Inspector (POI). This GC expires 1/24/2017.


Water and Waste Systems on Air Carrier Aircraft






PL-83, Revision 7, dated January 24, 2013

PL-83, Revision 6, dated December 17, 2012

PL-83, Revision 5, dated January 18, 2012

PL-83, Revision 4, dated October 15, 2001

PL-83, Revision 3, dated January 22, 2001

PL-83, Revision 2, dated October 13, 1999

PL-83, Revision 1, dated August 15, 1997

PL-83, Original, dated June 07, 1997


To provide standardized MMEL requirements for water and waste systems on air carrier aircraft.


Revision 8 removed all references to wheelchair accessible lavatories.

Revision 7 Clarifies repair category C relief includes wheelchair accessible lavatories. Revision 6 erroneously implied repair category C relief did not apply to wheelchair accessible lavatories.

Revision 6 removed MMEL relief associated with wheelchair accessible lavatories; removed all reference to cancelled MMEL PL-128.

Revision 5 removes the requirement for a forward/upper deck lavatory to be operative for dispatch. This requirement was established in late 2001 in response to recommendations for improved flight deck security. Since that time, numerous security initiatives have been implemented which mitigate the need for this restriction. Additionally, the restriction can only be applied to aircraft equipped with a forward/upper deck lavatory, thereby, unduly restricting operation of these aircraft when aircraft without a forward/upper deck lavatory may be operated. Revision 5, corrects DOTís position stated in the PL.

Revision 4 added proviso b) to the last set of provisos for Lavatory Waste Systems allowing the pilot-in-command the authority to decide if flight duration is acceptable with the forward/ upper deck lavatory unusable. This addition was a result of enhanced security requirements adopted by air carriers.

Revision 3 discussed the applicability of MMEL relief for wheelchair accessible lavatories.

Revision 2 clarified that the draining of potable water or toilet systems is not required if the system is deactivated such that no leaks are present. This allows operation of certain model airplanes without disabling the entire system.

Revision 1 reformatted P-83 with no change to policy. National Aviation Safety Inspection Program (NASIP) reports have revealed that there are differences in the manner in which some air carriers are deferring lavatories and potable water systems. In some instances relief is provided under the passenger convenience items, ATA section 25, or in ATA section 38. Differences also surfaced in the repair category where "C" was assigned in some instances and "D" in others for inoperative lavatories and potable water systems. Additionally, maintenance procedures (M) for these items, are not included the majority of MELs and air carrier maintenance manuals.

Considering the varied differences in the manner in which inoperative lavatories and potable water systems are managed, it has been recommended that a standard procedure be established for deferring these items in the MMEL/MEL.

This recommendation has been reviewed by the Aircraft Evaluation Groups for large transport category aircraft and it was agreed that standard MMEL relief along with maintenance (M) procedures should be reinstated for lavatories and potable water systems for all transport category airplanes. An (M) procedure is necessary so appropriate procedures will be included in the operators maintenance manual. The concerned aircraft manufacturer's Dispatch Deviation Guide should include appropriate procedures for operations with these items inoperative. In addition to the differences discussed above, there is concern with overflow problems, water accumulations in lower areas and bays along with follow-on corrosion problems, which could be prevented if (M) procedures are defined and followed.

The need for potable water and lavatory systems is incumbent on each air carrier/operator to assure that these items are adequately provided for its passengers. The lavatory systems referenced in this case are those units specifically for the relief and comfort of persons (i.e. the toilet).

Recent review of the manner in which some air carriers defer potable water and waste systems has shown a need for a MMEL standard for these systems and to provide for an (M) procedure for these items. ATA Chapter 38 is designated as the appropriate MMEL section for Potable Water Systems and Lavatories for Transport Category Airplanes. Air carrier/operator maintenance manual's chapter 38 should contain the maintenance procedures on a given system to effect MEL relief and tracking.


This establishes a standard MMEL relief for "Lavatory Systems" and "Potable Water Systems" for transport category airplanes. The following provisions provide a generic set of provisos that should be used as guidance in the development of individual model MMELs.

Note: This generic phraseology is only a guide and should be amended as appropriate for specific potable and waste water systems.



Repair Interval

Number Installed

Number Required for Dispatch

Remarks or Exceptions



Potable Water Systems




(M) Individual components may be inoperative provided:

a) Associated components are deactivated or isolated, and

b) Associated system components are verified not to have leaks.

Note: Any portion of system which operates normally may be used.






(M) May be inoperative provided:

a) System is drained, and

b) Procedures are established to ensure that system is not serviced.


Lavatory Waste Systems




(M) Individual components may be inoperative provided:

a) Associated components are deactivated or isolated, and

b) Associated system components are verified not to have Leaks.

Note: Any portion of system which operates normally may be used.






(M) Associated lavatory system may be inoperative provided:

a) Associated components are deactivated or isolated to prevent leaks, and

b) Associated lavatory door is secured closed and placarded, INOPERATIVE Ė DO NOT ENTER.

Note: These provisions are not intended to prohibit inspections by crewmembers.


Each Flight Operations Evaluation Board (FOEB) Chair should apply this policy to affected MMELs through the normal FOEB process.





Leslie H. Smith

Manager, Air Transportation Division