Tank Bolts have been shown to be long-lasting, and the 5/16" x 2 3/4" length will suit most brands and models. The bolts can be used on all metal tanks (not just PEX) and they can be installed from both sides of the tank. They can also be removed by hand in case of an emergency. There are two types of Tank Bolts: compression-type and expansion-type. Both work by using a washer and nut to hold the tank down to the bowl. The only difference is that the expansion bolt has a hollow center and is covered with rubber or another elastic material, which allows it to expand when tightened down over a pipe or other object. This article focuses on compression-type tank bolts. These bolts use a washer and nut to hold the tank down to the bowl. On older homes with steel tanks, compression-type bolts are usually made of brass or stainless steel and measure 5/8" or 3/4" in diameter. These bolts go through the floor first and then into the tank. They are easy to install and remove without any tools needed. Modern homes with PEX water tanks often use plastic compression-type bolts that are either coated in stainless steel or colored black.