Joining different sized downpipes

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    • #279563

      I have 100*75 colorbond (galv/zincalum) downpipes that need to join into a 100*50 pvc pipe. The plumber used a 100*50/100dia PVC adapter then a 100 dia pvc adapter to 100*75 PVC adapter Besides looking messy it leaks. What I was after is a 100*75 to 100*50 PVC or galv adapter.

      Are they available I can get 1 made by a fabrication firm but better if they are “on the shelf”

      Any thoughts appreciated

    • #301185
      Retired plbg1

      If that is threaded pipe you can buy gal. reducers or a coupling and a bushing. If it is plain pipe ypu can buy fernco coupling, look it up on internet. Let me know.

      Art retired plbg

    • #301186

      Sorry It is house stormwater downpipe , very thin (0.4mm) sheet steel and not round or capable of being threaded but 100mm by 75mm joining to 100mm by 50mm rectangular.

      the fitting has to be fabricated unless someone makes it as standard. To give you and idea see Look at page 3. the pipes are standard size here in Australia just that I concreted my 100*50 pipe into my path and do not want to cut it up.

      the plumber used 100*75 for the new pipe.

      btw thanks for taking the trouble to reply

    • #301187
      Retired plbg1

      Use fernco couplings, look them up on Google.

      Art retired plbg

    • #301188
      Robert Stephen Morton

      ternert. your description suggests the stormwater is constructed of pvc rainwater downpipe, to connect a 100×75 d/p to a smaller 100×50 stormwater doesn’t make any hydraulic sense. & hence no fitting is available.
      you would have more luck replacing the 100×50 stormwater (rainwater downpipe) with 90mm stormwater pipe which has fittings to convert, however the 100mm 75 D/P has a cross sectional area of .0075mm2 whereas the 90mm is .00648mm2 & 100mm is .008mm2.
      100mm would be the size that I would use.
      Do it yourself is always frought with failure.

      Regards bob

    • #301189

      The 100*75 was installed by a plumber I should have said no but he said he could join the 100*75 to the 100*50 PVC easily. the 100*75 is sheet gavanised steel

      My problem was i had concreted the 100*50 into quite a thickness of concrete mowing strip The thickness was to stop water entry into the house.Will check the ferco couplings but are they availble for rectangular couplings?


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