GB-75

Frequently Asked Questions

Are the Great Basin® indoor/outdoor units traffic rated (H-20 load rate)?

These units are traffic rated if they are installed in accordance with our installation instructions. The unit will need the H-20 load-rated cast iron covers and a traffic-rated pad at grade per our installation detail.

Can corrugated pipe be used as a riser on the Great Basin® indoor/outdoor units?

A 24" double wall corrugated pipe can be used as a riser for these units. You will need to purchase Schier's adapter for 24" corrugated pipe riser (CA2).

Can the discharge from a food waste grinder be run through the Great Basin® indoor/outdoor units?

These units have solids capacity of 20% or more of the unit's liquid volume, but food waste grinders can quickly overwhelm a grease interceptor. If the food waste grinder is connected to the unit, we recommend a solids interceptor in front of the grease interceptor.

Can the Great Basin® indoor/outdoor units be installed above grade (on the ground)?

All Great Basin® indoor/outdoor models can be installed above grade. The the adapter tie down kit (ATD1) is recommended to ensure the adapters do not become unseated in the event of a downstream backup. A GB-500 installed above grade must also have the above grade support kit (AGS2).

Can the Great Basin® units be used with a dishwasher?

These units can be used with a dishwasher. If the dishwasher will have a discharge temperature higher than 150 degrees Fahrenheit, the system will require a drain tempering valve to reduce the water temperature.

Can you suspend the Great Basin™ indoor/outdoor units from the ceiling above?

These units can be suspended from above (with the exception of GB-1000 and GB-1500). The unit needs to be fully supported across the bottom with risers extending to the floor above. It is the responsibility of the specifying engineer or installer to design a support system appropriate for the weight of the unit with water. If suspending a GB-250, the unit must be installed with the above grade support kit (AGS1). If suspending a GB-500, the unit must be installed with the above grade support kit (AGS2).

Do the Great Basin™ indoor/outdoor units need to be installed inside a vault to be buried in a high-water table area?

If the units will be installed in an area where the water table will crest the inlet/outlet pipe, additional steps need to be taken to protect the unit from the extreme hydrostatic forces. The unit would need to be placed in a water tight vault or encased in concrete. If there is a possibility that ground water will come into contact with the unit, there needs to be a high-water/anti-flotation anchor kit installed (AK1, AK2, AK3).

Do the Great Basin® units require a fixture vent?

These units do not require a fixture vent. The internal design of the unit will ensure proper function without a fixture vent. Any venting to the piping connected to our unit is at the discretion of the local authority.

How much space is needed between units when they are installed in series?

There should be a minimum of 6" between the units when installed in series. In a buried application, this space will ensure there is enough backfill in between the units.

Our fixture has an air gap and discharges into a floor sink, which is overflowing. How can we fix this?

Due to the low head pressure in this scenario, the first solution is to remove the internal flow control. This low head pressure ensures the unit will not exceed its certified flow rate. If that doesn’t solve the issue, the next solution is to add a flow restrictor to the tailpiece of the fixture.

What are the minimum and maximum riser heights of buried Great Basin™ indoor/outdoor units?

The adjustable adapters that ship with these units offer up to 4" of built-in riser height. The maximum height for field cut risers is 94," which is equivalent to three FCR2 risers (sold separately). If the unit is suspended with risers to the floor above, they can use more than three if needed.