<t:form t:clientValidation="none">
...will disable client validation on your form.
You can also do clientValidation="submit" which validates on submit rather than onBlur, you might try that?
More info:
http://tapestry.apache.org/current/apidocs/org/apache/tapestry5/corelib/components/Form.html http://tapestry.apache.org/5.3.7/apidocs/org/apache/tapestry5/corelib/ClientValidation.html