Encasing and Scour valve tee fitting in Ductile Iron pipe line

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Encasing and Scour valve tee fitting in Ductile Iron pipe line., Where are we do encasing of Ductile Iron pipe line?, Where are we use Scour valve in Ductile Iron pipe line?, What is the function of Scour valve in Ductile Iron pipe line?, What is purpose of encasing on Ductile Iron pipe?, Why we use Scour valve in ductile iron pipe line?
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