How to Replace a Toilet Riser Tube

When plumbers refer to the toilet riser tube, they also mean the fill valve, because both are parts of the same component. Water enters the bottom of the riser tube, where it is connected to the water supply, and exits through the top. The float is connected to the fill valve attached to the tube and shuts it when the tank fills. When the fill valve wears out and doesn't shut off completely, the tank can overfill and allow water to drain into the overflow tube. Replacing the riser stops this wastage and isn't difficult to do.


Turn off the water to the toilet by shutting off the valve jutting out from the wall or floor under the tank. Flush the toilet and hold down the handle to drain the tank. Sponge out the water remaining in the bottom.


Place a bucket under the tank to catch water and disconnect the supply tube from the toilet tank. You may be able to do it by hand, but if not, turn the nut connecting the supply hose to the bottom of the tank with adjustable pliers.


Loosen the nut above the one you just removed with a wrench. It's the nut holding the riser to the tank. Hold the riser with your other hand, or get a helper to do it, so it doesn't turn along with the nut. If corrosion is locking the nut, spray lubricant on it to loosen it. If that doesn't work, you may have to saw it off with a hacksaw. If so, saw carefully to avoid damaging the tank.


Unclip the rubber fill hose from the overflow tube and lift out the riser when the nut has been removed.


Measure the distance from the bottom of the tank to the top of the overflow tube with a tape measure and adjust the new riser so the critical level ring, which is marked "CL," is that distance plus 1 inch from the bottom. You usually adjust the length of the riser by twisting it.


Fit a rubber washer to the bottom of the riser and insert the riser into the hole in the bottom of the tank. Place a second washer over the threads underneath the tank and screw on the retaining nut. Hold the riser straight while you tighten the nut with an adjustable wrench.


Screw the flexible supply hose onto the riser from underneath the tank and tighten it by hand or with adjustable pliers. When the riser is secure, clip the rubber hose on top of it to the overflow tube. The tube should be pointed into the tank so water doesn't spray from under the tank cover.


Turn on the water and let the tank fill. Adjust the float so that the valve shuts off when the water level reaches the fill mark on the riser tube. When the tank is full, check underneath it for leaks. If you see any, tighten the riser nut or the water supply connection until they stop.