How about 28 gallons?
Jim,I managed to move from our 18 gal bucket to a 28 gallon tank in the same location. I could have spent more $ and obtained 30+ by usage of a custom tank, but the return on investment for the extra few gallons didn't look inviting. The install is very tight, but a standard tank can be fitted. I replaced mine because the vent line nipple was cracked and it didn't have a cleanout. I purchased the tank from Peggy, from a list of 100's of sizes available. Used Sealand Oderproof and have been very happy with the resultant capacity increase and lack of odor.Jeff JonesH34 Escapade