Some fan speculate this as a weapon that Russia uses towards others. Though he uses it to store things in it in the manga.
Because Russia was slow to industrialize, he was amazed by the faucet pipes that other nations had. It produced 'clean' running water, but only if it was still attached to the other pipes that carried the water. (If you see the lyrics of his character song "My Heart Has A Light", 'Then-then-then now, let’s open the faucet Hum, that’s strange, water won’t come out at all!', he thought that water always came out of the faucet by magic.