Troubleshooting a New Tub/Shower Valve Installation Learn how to fix common tub or shower valve installation issues Changing a tub and/or shower valve can be one of the more challenging plumbing projects for a DIY-er. Even when everything looks to be perfect, it's only after the water is back on and the handle is turned that you know whether or not to celebrate. Should your triumph be delayed, don't worry! We've compiled a few possible solutions for the most common post-installation issues with a new valve: little or no water coming out. Are the supply shut-offs in the "on" position? It sounds silly, but it happens! Did you make sure to flush the valve before installing the cartridge? This removes any sediment or debris that may have found its way into the supply lines or valve. If the valve isn't flushed, this debris can build up and create blockages, resulting in a reduction in pressure, little or no water, or only hot or cold water. Remove the cartridge, clear out any obstructions from it and the valve, and turn on the water for a minute to flush out any debris that may still be in the valve where you can't see it. Make sure you have the shower door closed during all of this - water will shoot out of the valve at your normal house pressure. If you're using a shower curtain, you may want to have someone help you: have them be ready with a bucket or pan to deflect the water and keep it confined to the tub/shower area as you turn the water on. We do not recommend anyone try to deflect the water with just their bare hands, as hot water scalding could be a risk. After reinstalling the cartridge, normal flow should be restored. If debris in the valve or cartridge isn't the issue, try removing the shower head and turning the water on to flush the riser pipe - just be sure to aim the water towards the drain, or have a bucket handy! This should clear any blockages on the way to the shower head. While you have the head off the arm, you can also clean out any screens or flow restrictors. Does the valve have service or screwdriver stops? Make sure they're both fully turned to the "on" position. Does your valve have a temperature stop, or temperature limiter? An incorrectly adjusted temperature stop can lead to water output that's too hot or too cold. The faucet installation instructions should have details on how to correctly set the temperature level for your shower. Sometimes, only the cold water is turned on to test for leaks, with the hot water being left off until everything is "ready to go". With a pressure-balance valve, if only one side has pressure (in this case, the cold side), the valve will do what it's designed to do and compensate for the lack of pressure on the other side. This results in either no water, or only a trickle making it through. Be sure that both hot and cold supplies are turned on! If everything is open and the valve still isn't functioning properly, try removing the pressure-balancing spool found inside the valve. When shaken, the unit should rattle. If it doesn't, try soaking it in a 1:1 vinegar/water solution to break up any blockages. If it's still stuck, you'll need to replace the spool. Make sure the handle and any handle stops have been installed or adjusted properly and in the correct orientation - otherwise, the handle may not rotate the cartridge correctly. If you have a hot water recirculation system and aren't getting any water at the shower, you'll want to check the system's air relief valve (or air vent, air eliminator, or purger). When the system is opened (to install the new tub/shower valve) air can find its way into the circulation line, become trapped, and stop flow. Opening this valve will allow that air to escape. If you have an automatic air vent, it could be plugged or malfunctioning. Hot and cold water reversed? With most valves, you can simply rotate the stem and/or the cartridge 180° to fix the problem. Still having problems? Consider posting about your situation at Plbg.com - if one of the DIYers there hasn't encountered the very same issue, chances are a few of the plumbers have!