We have currently constructed a drywell that works great for us. We are using it to drain the runoff from cleaning our kennel (no poop just the wash water). We also have a washing machine and sink draining into the system so ours is probably larger than most people would need, but we wanted to be certain it would have plenty of capacity so we would not have to do any rework later. ( I am not particulary fond of digging holes.) We constructed ours for around $150. It has a 220 gallon capacity. (Four 55 gallon food grade drums.) Here is the basic concept of what we made: 4/ 55 gallon thick pvc plastic barrels that contained corn syrup from a local candy maker (we did not want to use any that may have contained mysterious chemicals) $15 each. We dug a very large hole that was deep enough that the top of the barrels were two feet lower than grade. ($40 to hire neighbor with backhoe.) We drilled holes throughout the drums with a 1 inch spade bit and a 3/4 drill bit in random patterns (tedious but not difficult)We lined the entire hole with building paper. Covered the bottom with a foot to six inches of large gravel making sure all the barrels were level with each other, connected all of the barrels with 3" pvc pipe about 6" from the top of each barrel and had one barrel accepting the incoming 3" drainage pipe 2" from the top of the barrel. we then filled the remaining space around the barrels with the large gravel, covered the gravel with building paper and covered the building paper with dirt. It has worked silently without any problems for over a year and we wash and rinse the kennel twice daily as well as do laundry and have one sink connected. We left about two feet of space between the side of the hole and the sides of the barrel to fill with gravel to provide plenty of room to drain. Just a note though we have sandy loam soil so it drains very well in itself. If a person has heavy clay, they may want to connect a 20' black slotted pipe to one the barrels and use it as a pseudo leach field by running the pipe through a ditch filled with gravel and covering the ditch with building paper.
Hope this helps!