I知 working on building my shop / office for my farm. I知 about to go apply for a permit on the septic system but I need a design. The building has 2 full bathrooms, a sink for a food fixing area (fridge and microwave), and 2 utility sinks. The floor drains, utility sinks, and showers are on a gray water system.

Code calls for 2 tanks and an aerator (sp) in the second tank for houses. I can skip the aerator for this because this building will not see continues use. We do have to get a pump done every 5 years by code.

I知 thinking I should go with 1000 primary and a 500 secondary tank witch would be smallest by code I could use. I知 planning on using the half moon plastic leaching field system also. Were a family of 5 and can see us spending time around the shop in the summer a few days a week so I知 sure it will be used for the bathrooms and for cleaning up after being out side all day long. I can also see family gatherings a few times a year.

I知 thinking 3.5 gallons to flush and wash your hands. If every one went 4 times in 8 hours would give us 20 rounds on a normal day. So 70 gallons a day for normal times but for family get-togethers I would say 57 rounds in the bathrooms witch would put us at 199.5 gallons per day, but this would only be a few times a year.

Should I use 100, 150, or 200 as my number for sizing this systems leaching field? I do not want to have issues with this down the road. I want to do it right the first time.

Is there a better way to come up with this number (they want to see how I got the number)?

Any other suggestions that everyone over looks?