Are you sure they aren't young roaches (or water bugs)? That would seem more likely to me since they are accumulating around water drains. I've experienced this problem living in old homes, where there are plumbing leaks under the bathroom (you might want to have that checked out). Fixing leak took care of the problem. Roaches tend to come into homes in search of water sources, especially when rainfall is deficient.
"Oriental Cockroach. Oriental Cockroaches, Blatta orientalis (L.), are large very dark (almost black, but sometimes dark reddish-brown), shiny cockroaches which live in sewers and similar wet, decaying organic matter. They are sometimes called â€œwater bugsâ€ because they come out of drains, and â€œblack beetle cockroachesâ€ because of their smooth, dark bodies. Adult Males are about 1 inch long, with wings that cover only about Â¾ of their abdomen; Adult females are about 1 Â¼ inch long, and have only short stubs of wing pads. They survive best at lower temperatures than the other three urban pest roach species, preferring a range of 68 to 84oF (20 to 29oC), and are seldom found in warmer states in the U.S. They grow slowly, needing more than 200 days to go from hatching to adult, and females take another 60 days to produce their first egg capsule of 16 eggs. They may go on to produce 8 to 10 egg capsules at a rate of about one every 30-40 days, depending on temperature and moisture conditions. "
Obviously, I can't be sure what the problem actually is, or if they're actually beetles without seeing them, but I'll post the basics of organic roach combat just in case.
Clean up is a must: If cockroaches are a problem for you, make sure to seal up food products tight. Clean the crumbs from between the counters and refrigerator, and scrub down your counters and floors.
Seal cracks: Seal cracks along entry walls and windows to limit points of entry to your home.
Trap them: Use nontoxic sticky traps to trap the roaches. Use 8-10 traps around the perimeter of your kitchen, or whatever room seems to be a problem for you. You can make your own non-toxic bait by mixing Arm and Hammer detergent in a 50/50 mix with sugar. You can make boric balls by mixing 1 teaspoon of boric acid, 1-cup flour, Â½ cup sugar and Â½ cup water. Roll the mixture into cakes and place behind appliances out of the reach of children and pets.
Treatment: Apply a light dusting of boric acid or natural diatomaceous earth along cracks and crevices, or wherever roaches seem to be a problem. Boric acid is a potent stomach poison for many insects, but is safe to use around humans. Boric acid in its pure form is toxic if it is ingested. Make sure to use a dust mask when applying the powder form). Boric acid disrupts the action of bacteria in the stomach of the insect and causes the insect to starve to death. The entire process may take 5 to 10 days. A single application of boric acid will remain active for years as long as it remains dry. Natural diatomaceous earth (DE) is a mined product made up of the fossilized remains of tiny single-celled creatures called diatoms. It is abrasive and absorptive to insect exoskeletons. DE is virtually harmless to mammals, but its best to wear a dust mask when spreading it. (Do not use pool-grade DE for pest control. Pool-grade DE can cause serious respiratory problems and should not be used for organic pest control).