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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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 RwbbNBQyD5dsNRvQPtHl7A==

<SEC-DOCUMENT>0001063339-07-000001.txt : 20070426
<SEC-HEADER>0001063339-07-000001.hdr.sgml : 20070426
<ACCEPTANCE-DATETIME>20070426123848
ACCESSION NUMBER:		0001063339-07-000001
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20070424
FILED AS OF DATE:		20070426
DATE AS OF CHANGE:		20070426

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			SOUTHWEST WATER CO
		CENTRAL INDEX KEY:			0000092472
		STANDARD INDUSTRIAL CLASSIFICATION:	WATER SUPPLY [4941]
		IRS NUMBER:				951840947
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		ONE WILSHIRE BUILDING
		STREET 2:		624 SOUTH GRAND AVENUE, SUITE 2900
		CITY:			LOS ANGELES
		STATE:			CA
		ZIP:			90017-3782
		BUSINESS PHONE:		213 929 1800

	MAIL ADDRESS:	
		STREET 1:		ONE WILSHIRE BUILDING
		STREET 2:		624 SOUTH GRAND AVENUE, SUITE 2900
		CITY:			LOS ANGELES
		STATE:			CA
		ZIP:			90017-3782

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	SUBURBAN WATER SYSTEMS
		DATE OF NAME CHANGE:	19751202

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			NEWMAN RICHARD G
		CENTRAL INDEX KEY:			0001063339

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-08176
		FILM NUMBER:		07790246

	BUSINESS ADDRESS:	
		STREET 1:		AECOM TECHNOLOGY CORP
		STREET 2:		3250 WILSHIRE BLVD 5TH FL
		CITY:			LOS ANGELES
		STATE:			CA
		ZIP:			90010
		BUSINESS PHONE:		626-915-1551

	MAIL ADDRESS:	
		STREET 1:		AECOM TECHNOLOGY CORP
		STREET 2:		3250 WILSHIRE BLVD 5TH FL
		CITY:			LOS ANGELES
		STATE:			CA
		ZIP:			90017
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2007-04-24</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000092472</issuerCik>
        <issuerName>SOUTHWEST WATER CO</issuerName>
        <issuerTradingSymbol>swwc</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001063339</rptOwnerCik>
            <rptOwnerName>NEWMAN RICHARD G</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>AECOM TECHNOLOGY CORP</rptOwnerStreet1>
            <rptOwnerStreet2>3250 WILSHIRE BLVD 5TH FL</rptOwnerStreet2>
            <rptOwnerCity>LOS ANGELES</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>90017</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2007-04-24</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>10128</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>6.17</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>83968</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Director Stock Options (Right to Buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>6.17</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2007-04-24</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>10128</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2001-05-23</value>
            </exerciseDate>
            <expirationDate>
                <value>2007-05-24</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>10128</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">On May 23, 2000 10,128 options (dividend-adjusted) were granted to Mr. Newman. Options vest 1/2 each anniversary until they were fully vested on May 23,2002.</footnote>
        <footnote id="F2">These shares are held in joint trust for the benefit of the person's family: Richard G. Newman TR UA F/B/O R&amp;C Newman Revocable Trust.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Richard G. Newman</signatureName>
        <signatureDate>2007-04-26</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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