NOTICE* The external holes for the pipes in the rear box are made slightly larger than 1.5" PVC Pipe. They are designed to fit 40mm JIS pipe as well (Metric). They may be loose fitting with US Imperial PVC. This is normal. Some imperial PVC pipe or fittings may seem very loose, again this is normal. The pipes will glue in perfectly fine. Once glued, the glue will fill in the space between the Pipe and overflow hole when glued and will seal fine and not leak. Just look into the fitting as you are gluing it in place and look for any gaps.
You can use 1.5" PVC directly into the bottom of the overflow. Or you can reduce it down to 1" if needed with 1.5" to 1" PVC Reducers. We recommend for systems with LOW FLOW rates (under 1500 GPH) to reduce the pipes down to 1". The flow rate of the overflow will be less than 1500 GPH if reduced to 1" drains. The full 1.5" drains are better for higher flow systems, but can used with low flow systems without any issues as well.
Attach 3 short pieces (approx. 4”) of 1.5” PVC to the bottom of the rear box. (4” Pre Cut kits are available here). If using 1" PVC you will need 3 x 1.5" to 1" Reducers. You can glue them directly into the bottom of the rear box. Your internal pipes can stay 1.5" and do not need reducers.
This shows how to glue in the PVC Pipes
We recommend you using Medium or Heavy Clear PVC Cement on outside of the rear box when gluing the PVC pipes to it. We have found that any PVC Cement will work, but care needs to be used when gluing to make sure the ports do not get excessive glue inside the openings. If the proper amount of glue is used it will not take any force to push the pipes into the ports. See figure A.2 Below:
We recommend that you attach 3 x 1.5” Unions (3 x 1" if you have reduced the pipes to 1") to the 3 pieces you just glued into the bottom of the rear box. This will allow for easy removal of the overflow if needed in the future or for moving the overflow to another tank later. Unions are not necessary but make for a better installation.
Make sure to support the external plumbing properly to avoid any weight pulling down on the overflow rear box. The overflow was NOT designed to have the plumbing hanging from it. This can cause small leaks near the gaskets. We sell a few different pipe hanging clips here: 1.5″ Clic Clip or 1" Clic Clips that can assist with securing the external pipes to your aquarium stand.
We do NOT recommend using flexible PVC or vinyl tubing on the drains. The quietest operation will be using rigid PVC. Flexible PVC or Vinyl tubing also can reduce the flow rate of the overflow significantly!
