Since a standard builder’s hammer is more common than a rubber mallet and the rules call for a standard hammer, the standard hammer should be used.  If you need to soften the blow of the hammer, one suggestion is to put a scrap piece of wood between your object and the blow of the hammer.

Yes, you can fit pieces together to check fittings and cuts but everything must be disassembled before the prep phase is over.

The cost for the tools used during the build will be calculated based upon how long the operator(s) were in the 10’x10’ area.  If it takes 10 minutes to build your system, all of the tools used will be pro-rated for those 10 minutes.  For example, if you use a pipe wrench ($5.00 per unit-hour), and the build takes you 10 minutes, the cost for the pipe wrench is ($5.00/60 minutes)*(10 minutes) = ($0.083/minute)*(10minutes) = $0.83.

The build time will be timed for each team and yes, these times will later be added to your scores.

Yes, each team needs to provide an effluent catch basin for their system.  Please make the container big enough to capture just over 10-gallons of effluent, as the first gallon will be poured back into the rest of the collected effluent, and there will be the option to prep your systems with 0.25 gallons of tap water.

Since gravel is not on the list, it is considered a bonus item.

Prices need to be used from the list provided in the rules – that way, everyone has a fair advantage on cost.  Your prices can be changed in your report to reflect that.

Materials that are listed in the design report already should remain in the system.  Please refer to this previous answer on the website, date March 1, 2011: “All materials listed in the design report should be present and functional on the system.  However, changes in the quantity of items may be changed – testing and redesign should be done within the downtime before competition so that your system is designed more efficiently.  Reduction in the amount of chemical, the use of lumber, etc. should be looked at and is okay for the final design brought to competition.”

Since a caulking gun would need caulk to operate, these are not two separate items.  The operating cost would just be the $2.00 per unit-hour for caulk and the caulk gun.