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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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 CW3kbercWG9zJfMl6u/Rbw==

<SEC-DOCUMENT>0000077360-03-000159.txt : 20030915
<SEC-HEADER>0000077360-03-000159.hdr.sgml : 20030915
<ACCEPTANCE-DATETIME>20030915140930
ACCESSION NUMBER:		0000077360-03-000159
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20030912
FILED AS OF DATE:		20030915

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			HERNANDEZ WILLIAM H
		CENTRAL INDEX KEY:			0001189027

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-11625
		FILM NUMBER:		03895395

	MAIL ADDRESS:	
		STREET 1:		5500 WAYZATA BLVD.
		STREET 2:		SUITE 800
		CITY:			GOLDEN VALLEY
		STATE:			MN
		ZIP:			55416

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:		5500 WAYZATA BLVD.
		STREET 2:		SUITE 800
		CITY:			GOLDEN VALLEY
		STATE:			MN
		ZIP:			55416
		BUSINESS PHONE:		763-545-1730

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	PENTAIR INDUSTRIES INC
		DATE OF NAME CHANGE:	19790327
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>c0001189027d20030915f4f.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
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<ownershipDocument><schemaVersion>X0201</schemaVersion>    <documentType>4</documentType><periodOfReport>2003-09-12</periodOfReport><notSubjectToSection16>0</notSubjectToSection16><issuer><issuerCik>0000077360</issuerCik><issuerName>PENTAIR INC</issuerName>        <issuerTradingSymbol>PNR</issuerTradingSymbol></issuer><reportingOwner><reportingOwnerId><rptOwnerCik>0001189027</rptOwnerCik><rptOwnerName>HERNANDEZ WILLIAM H</rptOwnerName></reportingOwnerId><reportingOwnerAddress><rptOwnerStreet1>5500 WAYZATA BLVD.</rptOwnerStreet1><rptOwnerStreet2>SUITE 800</rptOwnerStreet2><rptOwnerCity>GOLDEN VALLEY</rptOwnerCity><rptOwnerState>MN</rptOwnerState><rptOwnerZipCode>55416-1259</rptOwnerZipCode><rptOwnerStateDescription></rptOwnerStateDescription></reportingOwnerAddress><reportingOwnerRelationship><isDirector>1</isDirector><isOfficer>0</isOfficer><isTenPercentOwner>0</isTenPercentOwner><isOther>0</isOther><officerTitle></officerTitle><otherText></otherText></reportingOwnerRelationship></reportingOwner><nonDerivati
veTable><nonDerivativeHolding><securityTitle><value>Common Stock</value></securityTitle><postTransactionAmounts><sharesOwnedFollowingTransaction><value>500</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></nonDerivativeHolding></nonDerivativeTable><derivativeTable><derivativeTransaction><securityTitle><value>Phantom Stock Units - Deferred Compensation</value></securityTitle><conversionOrExercisePrice><value>1</value><footnoteId id="F1"/></conversionOrExercisePrice><transactionDate><value>2003-09-12</value></transactionDate><deemedExecutionDate></deemedExecutionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>A</transactionCode><equitySwapInvolved>0</equitySwapInvolved><footnoteId id="F2"/></transactionCoding><transactionAmounts><transactionShares><value>23.132</value></transactionShares><transactio
nPricePerShare><value>40.5277</value><footnoteId id="F3"/></transactionPricePerShare><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><exerciseDate><footnoteId id="F4"/></exerciseDate><expirationDate><footnoteId id="F4"/></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common Stock</value></underlyingSecurityTitle><underlyingSecurityShares><value>23.132</value></underlyingSecurityShares></underlyingSecurity><postTransactionAmounts><sharesOwnedFollowingTransaction><value>600.442</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>I</value></directOrIndirectOwnership><natureOfOwnership><value>By Plan Agent</value></natureOfOwnership></ownershipNature></derivativeTransaction></derivativeTable><footnotes><footnote id="F1">Phantom stock units convert into common stock on a one-for-one basis.</footnote><footnote id="F2">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="F3">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="F4">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>2003-09-15</signatureDate></ownerSignature></ownershipDocument>

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