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cmphasizcd that thc air gap funncl asscmbly will handlc onl� the occasional spitting <br /> and will not conirol llow in a continuous rclief situatiun. <br /> K. 13ecause of the naiure of a reduced pressure backilow preventcr, Ilucmating supplp <br /> pressurc on an extremc low tlow or static flow condition may cause nuisancc <br /> dripping and eventual fouling of the assemUly. In a static condition, (i.e., an RPBA <br /> on the mokcup �.vnler line to a boiler) the reduccd pressurc zone betwcen Ihe Grst and <br /> sccond chcck v�lvcs must bc maintaincd at a 2.0 psi or grcatcr ditTcrential bclo��� thc <br /> supply pressure. Dcpending on the degrce of fluctuating supply pressure, the <br /> asscmbly may dischargc watcr from timc to timc. This hccomcs a nuisancc <br /> dischargc and can oventually causc o fouling of thc lirst chcck valvc. 11 is good <br /> plumbing practicc to n�commcnd a soft scatcd chcck va!vc immcdiatcly ahcad oC the <br /> RPBA which would hold the pressure constant to ihe valvc in times of (luctuating <br /> s�rr�y�«55����. <br /> L. Sizc the assemUly hydraulically to avoid cscessivc pressurc Ioss. Tlic hcad loss is <br /> not �eccssarily directly proportional to (low. Somc asscmblics have a higli hcad loss <br /> at low flows and a lotv hcad loss at high Ilows. <br /> n4. Good plutnbing practicc recommcnds a straincr wiQt blow out tappinb ahcad of thc <br /> assembly. <br /> N. I.:�rg:r sizc assemblies (I%i' and up) shall ha��c support blocks to prevent Oange <br /> damagc. <br /> O. TIInROUG}ILY I'I,USIi THC L1NCS PRIOR TO INSTALLING THG RPDA: <br /> L'.xperience has sho�vn diat a large majority of "failurc of test" results in new <br /> inslallations arc duc to dcbris fouling cithcr the fust or sccond chcck valvc scats. <br /> � <br /> '�`� _ <br /> \\ <br /> �� <br /> �r--:� i � : T� <br /> �\ e , � � <br /> " � I I �. � —I—b � <br /> � � _-�-:��� �*, — � „ , � <br /> �:��1.;--•��v-;- � � �_;� w� � <br /> �._, _.. -r--. <br /> � �. rv-� ���_'�r"� <br /> I ���- . �. <br /> N ' \ <br /> / � -� � �Oar <br /> ! � etp?E =�� � <br /> � � �� �.—�" ..�,'�vb;.•�l-:`F�'rm a'4°�• ,� <br /> ( � 7_! � ��:i ' � � � � <br /> `� g � <br /> o � <br /> 5:\BBruce\BackFlow Innallation RrquiremenLs 0217D9 Jm.da �`l� <br />