What is the difference between a divorce and a legal separation? Very Little. With one exception, the litigation process,  procedure and final result or conclusion are the same. The only difference is at the end of a legal separation case, there is a Decree of Separation rather than a Decree of Dissolution, such that the legal status of the marriage or being married is not terminated. But after six months have passed since the Decree of Separation was signed by the judge or commissioner, either spouse has an absolute right to convert the Decree of Separation into a Decree of Dissolution by way of a simple and inexpensive procedure.  There are no legal benefits that are preserved by way of a Separation Decree over that of a Dissolution Decree. For example, all group health insurance plans do not allow the employee to maintain  coverage for a Legally Separated spouse. A separated spouse in not an "heir" of the other spouse. Filing the case as a Petition for Legal Separation will not save any legal fees over a Petition for a Dissolution. A client may choose to have the case filed as a Separation for emotional or religious purposes and then elect to conclude the case as a Dissolution.  

Below are downloadable files of Petitions for Dissolution and Legal Separation and you can see there is very little difference. 

_PT Diss marriage.doc _PT Diss marriage.doc
Size : 123.5 Kb
Type : doc
_PT legal sep marriage.doc _PT legal sep marriage.doc
Size : 133 Kb
Type : doc

For a general guide to the marital dissolution process in Washington see the hand book written by the state courts here:   

http://www.courts.wa.gov/newsinfo/content/pdf/FLHBMarriageEdition.pdf  

There is also a handbook for domestic partnership dissolutions here:

  http://www.courts.wa.gov/newsinfo/content/pdf/FLHBDomesticPartnershipEdition.pdf   but keep in mind due to the passage in 2012 of the same sex marriage initiative, some of the domestic partnership laws will quickly be obsolete.