
<PAGE>


                                                                   Exhibit 5.1



June 12, 1997



Central Sprinkler Corporation
451 North Cannon Avenue
Lansdale, Pennsylvania  19446

Re: Central Sprinkler Corporation - Form S-8 Registration Statement Relating to
    the Central Sprinkler Corporation 1996 Equity Compensation Plan
    ---------------------------------------------------------------------------

Ladies and Gentlemen:

As your counsel, we have assisted in the preparation of the above-referenced
registration statement (the "Registration Statement") for filing with the
Securities and Exchange Commission pursuant to the Securities Act of 1933, as
amended (the "Act"), and the rules and regulations promulgated thereunder.

The Registration Statement relates to 800,000 shares of Common Stock, $.01 par
value (the "Common Stock"), of Central Sprinkler Corporation (the "Registrant")
which may be issued pursuant to the 1996 Equity Compensation Plan of the
Registrant (the "Plan"). We have examined the Registrant's Articles of
Incorporation, as amended, By-Laws, as amended, minutes and such other
documents, and have made such inquiries of the Registrant's officers, as we have
deemed appropriate. In our examination, we have assumed the genuineness of all
signatures, the authenticity of all items submitted to us as originals, and the
conformity with originals of all items submitted to us as copies.

Based upon the foregoing, it is our opinion that the Registrant's Common Stock
originally issued by the Registrant to eligible participants through the Plan,
when issued and delivered as contemplated by the Plan, will be legally issued,
fully paid and non-assessable.

We hereby consent to the use of this opinion as Exhibit 5.1 to the Registration
Statement. In giving such consent, we do not thereby admit that we are acting
within the category of persons whose consent is required under Section 7 of the
Act or the rules or regulations of the Securities and Exchange Commission
thereunder.

Very truly yours,


/s/Morgan, Lewis & Bockius LLP
-------------------------------
Morgan, Lewis & Bockius LLP


