Product review (5 stars): Mini-rester Water Hammer Arrester
A water hammer was built into this house by poor plumbing, and any number of plumbers sent by the builder were not able to solve the problem. They eventually reduced the water pressure to the house by putting a device inline with the house water inlet.  That device eventually rusted out, and I had to remove it.  I put the Mini-rester between the water outlet to the master bathroom toilet and toilet water inlet, and the problem was solved for the cold water pipes.  This toilet is the farthest point away from the water heater, which is in the garage.  During our master bath remodel, I'm having a mini-rester put in on the all the lines to the bathroom sinks.  I'm also having the contractors put Mini-resters, with male sweat connections, to the bath and the shower pipes.  It's overkill, but I don't plan to have any more water hammering in my house. I heartily recommend this product.