Monthly Archives: February 2014

What a beautiful wetback installation

2 guys and 8 hours later this wetback installation was compete. Quick recovery time by having a wetback ready hot water cylinder just above the wetback.

Some Essentials in the design of the flow and return pipes when it comes to wetbacks:


  1. Pipes connecting the wetback and the storage vessel must have adequate rise and fall. This will wetback-hwcallow convectional flow and prevent air locks. G12 AS1 states a minimum of 1 in 7 slope to ensure heat will transfer between wetback and storage heater by thermo siphon.
  2. Flow and return pipes should be in copper and generally be a minimum of 25mm diameter. AS/NZS 3500 part 4 section 7 includes a table to determine pipe size according to length of run. The open vent should be a minimum of 20 mm diameter.
  3. If the hot water cylinder is not positioned high enough above the heat source it is possible for reversed circulation to occur. Reversed circulation, also known as back circulation, takes place when heat is transferred from the water cylinder back to the heat source.
  4. The bottom of the water cylinder should be at least 300 mm above the heat source assuming the flow line is connected to a riser pipe or coil within the cylinder. If no riser is fitted a distance of at least 600 mm should be made between the two appliances.

To find out more about wetback and hot water cylinder regulations please visit our regulations page. If in doubt give us a ring and speak to a qualified technician 🙂