-----BEGIN PRIVACY-ENHANCED MESSAGE-----
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,
 KfU0jyE8y9uFU5pmaFoOHjonxLXrMy92Sa9YqefNFGTyG1E7UWW542bHMNeUhcki
 PlAqEf+NGG+Wxw06lrFLAg==

<SEC-DOCUMENT>0001058854-05-000115.txt : 20050520
<SEC-HEADER>0001058854-05-000115.hdr.sgml : 20050520
<ACCEPTANCE-DATETIME>20050520173310
ACCESSION NUMBER:		0001058854-05-000115
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20050519
FILED AS OF DATE:		20050520
DATE AS OF CHANGE:		20050520

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			NATCO GROUP INC
		CENTRAL INDEX KEY:			0001057693
		STANDARD INDUSTRIAL CLASSIFICATION:	FABRICATED PLATE WORK (BOILER SHOPS) [3443]
		IRS NUMBER:				222906892
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			0331

	BUSINESS ADDRESS:	
		STREET 1:		BROOKHOLLOW CENTRAL III
		STREET 2:		2950 NORTH LOOP WEST STE 750
		CITY:			HOUSTON
		STATE:			TX
		ZIP:			77092
		BUSINESS PHONE:		7136839292

	MAIL ADDRESS:	
		STREET 1:		BROOKHOLLOW CENTERL III
		STREET 2:		2950 NORTH LOOP WEST STE 750
		CITY:			HOUSTON
		STATE:			TX
		ZIP:			77092

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			CANNELL CAPITAL LLC
		CENTRAL INDEX KEY:			0001058854
		STATE OF INCORPORATION:			CA
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-15603
		FILM NUMBER:		05849234

	BUSINESS ADDRESS:	
		STREET 1:		150 CALIFORNIA STREET
		CITY:			SAN FRANCISCO
		STATE:			CA
		ZIP:			94111
		BUSINESS PHONE:		4158358300

	MAIL ADDRESS:	
		STREET 1:		150 CALIFORNIA STREET
		CITY:			SAN FRANCISCO
		STATE:			CA
		ZIP:			94111

	FORMER NAME:	
		FORMER CONFORMED NAME:	CANNELL J CARLO DBA CANNELL CAPITAL MGMT
		DATE OF NAME CHANGE:	19980330
</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>2005-05-19</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001057693</issuerCik>
        <issuerName>NATCO GROUP INC</issuerName>
        <issuerTradingSymbol>NTG`</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001058854</rptOwnerCik>
            <rptOwnerName>CANNELL CAPITAL LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>150 CALIFORNIA STREET</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>SAN FRANCISCO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94111</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2005-05-19</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>600</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>10.3167</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1658700</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2005-05-20</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>1400</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>10.3143</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1660100</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <ownerSignature>
        <signatureName>J. Carlo Cannell</signatureName>
        <signatureDate>2005-05-20</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
-----END PRIVACY-ENHANCED MESSAGE-----