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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
Originator-Key-Asymmetric:
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 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 IyCLPWUoK6SrX5qHCYiilCSDPKVLKRy6eLyGibYefBESer4MeEOKTh+XsYZ4eYHi
 /ve+u2Pz6Xs675O79NheYQ==

<SEC-DOCUMENT>0000077360-03-000097.txt : 20030513
<SEC-HEADER>0000077360-03-000097.hdr.sgml : 20030513
<ACCEPTANCE-DATETIME>20030513141704
ACCESSION NUMBER:		0000077360-03-000097
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20030509
FILED AS OF DATE:		20030513

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			HARRISON DAVID D
		CENTRAL INDEX KEY:			0001189046

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-11625
		FILM NUMBER:		03695045

	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>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>c0001189046d20030513f4f.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<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>0001189046</rptOwnerCik>            <rptOwnerName>HARRISON DAVID D</rptOwnerName>        </reportingOwnerId>        <reportingOwnerAddress>            <rptOwnerStreet1>  </rptOwnerStreet1>            <rptOwnerStreet2>  </rptOwnerStreet2>            <rptOwnerCity>  </rptOwnerCity>            <rptOwnerState>  </rptOwnerState>            <rptOwnerZipCode>  </rptOwnerZipCode>        </reportingOwnerAddress><reportingOwnerRelationship><isDirector>0</isDirector><isOfficer>1</isOfficer><isTenPercentOwner>0</isTenPercentOwner><isOther>0</isOther><officerTitle>Executive Vice President, CFO</officerTitle><otherText></otherText></reportingOwnerRelationship></
reportingOwner><nonDerivativeSecurity><securityTitle><value>Common Stock - ESPP</value></securityTitle><transactionDate><value>2003-05-09</value></transactionDate><transactionCoding><transactionFormType>5</transactionFormType><transactionCode>A</transactionCode><equitySwapInvolved>0</equitySwapInvolved><footnoteId id="F1"/></transactionCoding><transactionTimeliness><value></value></transactionTimeliness><transactionAmounts><transactionShares><value>24.277</value></transactionShares><transactionValue><value>38.6168</value><footnoteId id="F2"/></transactionValue><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><postTransactionAmounts><sharesOwnedFollowingTransaction><value>1029.777</value><footnoteId id="F3"/></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></nonDerivativeSecurity><footnot
es><footnote id="F1">Purchase of shares under the Pentair, Inc. Employee Stock Purchase Plan in exempt transaction pursuant to Rule 16b-3(c).</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">Reporting person also holds 54,484 shares directly; and 309.9675 indirectly by ESOP.  ESPP and ESOP balances include shares acquired under the Pentair, Inc. Dividend Reinvestment Plan in exempt transaction not required to be reported pursuant to Section 16(a).</footnote></footnotes><ownerSignature><signatureName>Louis L. Ainsworth, Attorney-In-Fact</signatureName><signatureDate>2003-05-13</signatureDate></ownerSignature></ownershipDocument>

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</SEC-DOCUMENT>
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