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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,
 WZhNqV3VQ1hgYgAdjettnSi9HGHrljJiQJVAFPWFtLxFLxX7A/vaDSFvgZ9qNocZ
 K3mPvkh7YHQMmz6M5rghfQ==

<SEC-DOCUMENT>0000077360-03-000169.txt : 20031014
<SEC-HEADER>0000077360-03-000169.hdr.sgml : 20031013
<ACCEPTANCE-DATETIME>20031014120503
ACCESSION NUMBER:		0000077360-03-000169
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20031013
FILED AS OF DATE:		20031014

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:		03938678

	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>c0001189039d20031014f4f.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<ownershipDocument><schemaVersion>X0201</schemaVersion>    <documentType>4</documentType><periodOfReport>2003-10-13</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>5500 WAYZATA BLVD.</rptOwnerStreet1><rptOwnerStreet2>SUITE 800</rptOwnerStreet2><rptOwnerCity>GOLDEN VALLEY</rptOwnerCity><rptOwnerState>MN</rptOwnerState><rptOwnerZipCode>55416-1259</rptOwnerZipCode><rptOwnerStateDescription></rptOwnerStateDescription></reportingOwnerAddress><reportingOwnerRelationship><isDirector>0</isDirector><isOfficer>1</isOfficer><isTenPercentOwner>0</isTenPercentOwner><isOther>0</isOther><officerTitle>President, COO Water Tech.</officerTitle><otherText></otherText></reportingOwnerRelationship></re
portingOwner><nonDerivativeTable><nonDerivativeHolding><securityTitle><value>Common Stock</value></securityTitle><postTransactionAmounts><sharesOwnedFollowingTransaction><value>47625.256</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></nonDerivativeHolding><nonDerivativeHolding><securityTitle><value>Common Stock</value></securityTitle><postTransactionAmounts><sharesOwnedFollowingTransaction><value>759.156</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>I</value></directOrIndirectOwnership><natureOfOwnership><value>By Children</value></natureOfOwnership></ownershipNature></nonDerivativeHolding><nonDerivativeTransaction><securityTitle><value>Common Stock - ESPP</value></securityTitle><transactionDate><value>2003-10-13</value></transactionDate><deemedExecutionDate></d
eemedExecutionDate><transactionCoding><transactionFormType>5</transactionFormType><transactionCode>A</transactionCode><equitySwapInvolved>0</equitySwapInvolved><footnoteId id="F1"/></transactionCoding><transactionTimeliness><value></value></transactionTimeliness><transactionAmounts><transactionShares><value>23.046</value></transactionShares><transactionPricePerShare><value>40.6787</value><footnoteId id="F2"/></transactionPricePerShare><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><postTransactionAmounts><sharesOwnedFollowingTransaction><value>2470.986</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></nonDerivativeTransaction><nonDerivativeHolding><securityTitle><value>Common Stock - ESOP</value></securityTitle><postTransactionAmounts><sharesOwnedFollowingTransaction><value>181
2.8444</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>I</value></directOrIndirectOwnership><natureOfOwnership><value>By ESOP</value></natureOfOwnership></ownershipNature></nonDerivativeHolding></nonDerivativeTable><derivativeTable></derivativeTable><footnotes><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></footnotes><ownerSignature><signatureName>Louis L. Ainsworth, Attorney-In-Fact</signatureName><signatureDate>2003-10-14</signatureDate></ownerSignature></ownershipDocument>

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