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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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MIC-Info: RSA-MD5,RSA,
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 CF9XRh12TzixC7oeTkbv0A==

<SEC-DOCUMENT>0000077360-03-000094.txt : 20030512
<SEC-HEADER>0000077360-03-000094.hdr.sgml : 20030512
<ACCEPTANCE-DATETIME>20030512154308
ACCESSION NUMBER:		0000077360-03-000094
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20030509
FILED AS OF DATE:		20030512

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			WELKE KAREN E
		CENTRAL INDEX KEY:			0001189034

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-11625
		FILM NUMBER:		03692806

	MAIL ADDRESS:	
		STREET 1:		1500 COUNTY ROAD B2 WEST
		CITY:			ST PAUL
		STATE:			MN
		ZIP:			55113-3105

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			PENTAIR INC
		CENTRAL INDEX KEY:			0000077360
		STANDARD INDUSTRIAL CLASSIFICATION:	SPECIAL INDUSTRY MACHINERY (NO METALWORKING MACHINERY) [3550]
		IRS NUMBER:				410907434
		STATE OF INCORPORATION:			MN
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		1500 COUNTY ROAD B2 WEST
		STREET 2:		SUITE 400
		CITY:			ST. PAUL
		STATE:			MN
		ZIP:			55113
		BUSINESS PHONE:		6516367920

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	PENTAIR INDUSTRIES INC
		DATE OF NAME CHANGE:	19790327
</SEC-HEADER>
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<TYPE>4
<SEQUENCE>1
<FILENAME>c0001189034d20030512f4f.xml
<DESCRIPTION>PRIMARY DOCUMENT
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<ownershipDocument>    <schemaVersion>X0101</schemaVersion><documentType>4</documentType><periodOfReport>2003-05-09</periodOfReport><notSubjectToSection16>0</notSubjectToSection16><issuer><issuerCik>0000077360</issuerCik>        <issuerName>PENTAIR INC</issuerName><issuerTradingSymbol>PNR</issuerTradingSymbol></issuer><reportingOwner><reportingOwnerId><rptOwnerCik>0001189034</rptOwnerCik>            <rptOwnerName>WELKE KAREN E</rptOwnerName>        </reportingOwnerId>        <reportingOwnerAddress>            <rptOwnerStreet1>  </rptOwnerStreet1>            <rptOwnerStreet2>  </rptOwnerStreet2>            <rptOwnerCity>  </rptOwnerCity>            <rptOwnerState>  </rptOwnerState>            <rptOwnerZipCode>  </rptOwnerZipCode>        </reportingOwnerAddress><reportingOwnerRelationship><isDirector>1</isDirector><isOfficer>0</isOfficer><isTenPercentOwner>0</isTenPercentOwner><isOther>0</isOther><officerTitle></officerTitle><otherText></otherText></reportingOwnerRelationship></reportingOwner><derivativeSecuri
ty><securityTitle><value>Phantom Stock Units - Deferred Compensation</value></securityTitle><conversionOrExercisePrice><value>1</value></conversionOrExercisePrice><transactionDate><value>2003-05-09</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>A</transactionCode><equitySwapInvolved>0</equitySwapInvolved><footnoteId id="F1"/></transactionCoding><transactionAmounts><transactionShares><value>80.384</value></transactionShares><transactionValue><value>38.6168</value><footnoteId id="F2"/></transactionValue><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><exerciseDate><value>1988-08-08</value><footnoteId id="F3"/></exerciseDate><expirationDate><value>1988-08-08</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common Stock</value></underlyingSecurityTitle><underlyingSecurityShares><value>80.384</value></underlyingSecurityShares></underlyingSecurity><postTransactionAmounts><sha
resOwnedFollowingTransaction><value>0</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>I</value></directOrIndirectOwnership><natureOfOwnership><value>By Plan Agent</value></natureOfOwnership></ownershipNature></derivativeSecurity><footnotes><footnote id="F1">Represents phantom stock units credited under a deferred compensation plan for non-employee directors over which the reporting person has no current dispositive or voting power.</footnote><footnote id="F2">Shares acquired under this Plan are purchased over a three-day trading period.  The price shown is the average purchase price over the trading period.</footnote><footnote id="F3">Settlement of phantom stock units will be in Pentair common stock in accordance with reporting person's irrevocable election.</footnote></footnotes><ownerSignature><signatureName>Louis L. Ainsworth, Attorney-In-Fact</signatureName><signatureDate>2003-05-12</signatureDate></ownerSignature></ownershipDocument>

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