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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,
 HE2jPzGQydAXLkXf+vK1OVcfTIuEw+y3puYKzn2V6UxbZwQBGZs1BHaasOKk7ads
 Obb11wjfSlrzcQz8cCNMNQ==

<SEC-DOCUMENT>0000077360-03-000095.txt : 20030513
<SEC-HEADER>0000077360-03-000095.hdr.sgml : 20030513
<ACCEPTANCE-DATETIME>20030513135943
ACCESSION NUMBER:		0000077360-03-000095
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:			CATHCART RICHARD J
		CENTRAL INDEX KEY:			0001189039

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-11625
		FILM NUMBER:		03694955

	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>c0001189039d20030513f4f.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>0001189039</rptOwnerCik>            <rptOwnerName>CATHCART RICHARD J</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>President, COO Water Tech.</officerTitle><otherText></otherText></reportingOwnerRelationship></r
eportingOwner><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>2341.088</value><footnoteId id="F3"/></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></nonDerivativeSecurity><footnote
s><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 47,404.558 shares directly; 758.162 indirectly by children; 1,802.4042 indirectly by ESOP.  Balances include shares acquired under the Pentair, Inc. Dividend Reinvestment Plan in exempt transactions 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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