--- title: "Water Hammer After a Hookup: Banging Pipes When a Valve Shuts: Causes and Fixes" description: "Water hammer after a hookup is a bang, knock or shudder in the pipes each time a newly connected appliance closes its water valve." url: "https://applianceinstallation.center/problems/water-hammer-after-hookup/" --- # Water Hammer After a Hookup: Banging Pipes When a Valve Shuts Water hammer after a hookup is a bang, knock or shudder in the pipes each time a newly connected appliance closes its water valve. ## What it usually means. Water moving through a pipe carries momentum, and when a valve slams shut, that moving column stops all at once and sends a pressure spike back through the plumbing. The sound is a single bang or a rattle in the wall. Modern appliances make it more likely than the ones they replace, because their inlet valves are electric solenoids that close in a fraction of a second, and a washer or a dish care machine opens and closes them many times per cycle. A new appliance in an old house is where it shows up: pipes that were never strapped to the framing, a supply line run straight to the valve with no slack, very high street pressure, or old air chambers in the wall that have filled with water over the years and no longer cushion anything. Refrigerators and ice makers can knock too, with each short fill. Water hammer is not an emergency, but it stresses the new connections, the valve on the appliance and the joints in the walls with every cycle. The fix is at the installation: water hammer arrestors fitted at the connection, supply lines with a gentle loop instead of a tight pull, and a check of the house pressure. Strapping pipes inside the walls is a plumber's job. The 6 causes, cheapest first Answer these first 01 Does the bang happen at the moment the appliance stops filling? 02 Is it a single knock, or a rattle that goes on for a second? 03 Did the old appliance make the same sound, or did it start with the new one? 04 Do faucets in the house bang when they are closed quickly as well? 05 Is the house on high street pressure, or does a pressure regulator sit near the main? ## Check these before you book. Water hammer after a hookup: 5 checks, and none of them costs anything. 01 Listen for when the bang happens: at the end of a fill, on a drain or on a spin. 02 Close a faucet quickly and see whether the house pipes bang on their own too. 03 Look at the supply line behind the appliance: is it pulled tight, or does it have a gentle loop? ### Also worth checking - If you have a hose bibb pressure gauge, check the house pressure. - Check the connections behind the appliance for any new drip after the knocking. ### How soon does it need a visit? Water hammer is not an emergency, but it strains the new joints. Keep an eye on the connections for drips, and if one appears, close the supply valve and treat it as a leak. ## The causes, cheapest first. 6 things water hammer after a hookup: banging pipes when a valve shuts turns out to be, from a supply line pulled tight to the valve to an inlet valve closing roughly. [The cost guide](https://applianceinstallation.center/cost/) 1. 01 lowest ### A supply line pulled tight to the valve A short line with no slack passes every jolt straight into the valve and the pipe. A line of the right length with a gentle loop softens it, and the joints stay unstressed. [Fixed by water supply and shutoff connection](https://applianceinstallation.center/services/water-supply-and-shutoff-connection/) [On a dish care machine](https://applianceinstallation.center/types/dish-care-installation/) 2. 02 low ### Fast-closing valves on the new appliance Solenoid inlet valves shut in an instant, and the water column slams. Water hammer arrestors fitted at the laundry or dish care connection absorb the spike. [Fixed by water supply and shutoff connection](https://applianceinstallation.center/services/water-supply-and-shutoff-connection/) [On a laundry machine](https://applianceinstallation.center/types/laundry-installation/) 3. 03 low ### Old air chambers full of water The capped pipes in older walls that once cushioned the flow fill with water over time. Draining the system can restore them briefly; arrestors at the appliance are the lasting answer. [Fixed by water supply and shutoff connection](https://applianceinstallation.center/services/water-supply-and-shutoff-connection/) [On a laundry machine](https://applianceinstallation.center/types/laundry-installation/) 4. 04 low to moderate ### High water pressure in the house Very high pressure makes every valve closure louder and strains the appliance's inlet. A gauge on a hose bibb shows it, and a pressure regulator near the main is a plumber's job. [Book a diagnostic visit](https://applianceinstallation.center/services/diagnostic-visit/) 5. 05 moderate ### Loose pipes behind the wall Pipes that are not strapped to the framing knock against it when the flow stops. Securing pipes inside the walls or floors is a plumber's work, and it can be combined with fitting arrestors. [Book a diagnostic visit](https://applianceinstallation.center/services/diagnostic-visit/) 6. 06 moderate ### An inlet valve closing roughly When arrestors, slack and pressure are all right and one appliance still knocks, its inlet valve may be closing badly. On a new unit that is the maker's warranty, and otherwise our sister repair site. [Book a diagnostic visit](https://applianceinstallation.center/services/diagnostic-visit/) ## What else it could be. Most often confused with water leak after an install: close the supply valve first, then drain backing up after an install: plug, loop and standpipe. [All problems](https://applianceinstallation.center/problems/) Codes that come with it - [`F12` ASKO · Water supply and drain](https://applianceinstallation.center/error-codes/asko-f12/) - [`E17` Bosch · Water supply and drain](https://applianceinstallation.center/error-codes/bosch-e17/) - [`Error 560186` Cove · Water supply and drain](https://applianceinstallation.center/error-codes/cove-error-560186/) - [`E:3200` Gaggenau · Water supply and drain](https://applianceinstallation.center/error-codes/gaggenau-e3200/) - [`F12` Miele · Water supply and drain](https://applianceinstallation.center/error-codes/miele-f12-water-inlet/) - [`E16` Thermador · Water supply and drain](https://applianceinstallation.center/error-codes/thermador-e16/) [1 more codes, by make](https://applianceinstallation.center/error-codes/) Also related - [**New Unit Vibrating or Walking Across the Floor** 6 causes](https://applianceinstallation.center/problems/new-unit-vibrating-or-walking/) Hazard after a hookup ### Water Leak After an Install: Close the Supply Valve First 6 causes ### Drain Backing Up After an Install: Plug, Loop and Standpipe 6 causes ### Ice Maker Not Filling After the Install: Valve, Line and Patience 6 causes ## The makes it happens on. 37 makes on this site; water hammer after a hookup: banging pipes when a valve shuts can show up on any of them. Each mark opens that make's own page. [All 37 brands](https://applianceinstallation.center/brands/) ## Water Hammer After a Hookup: Banging Pipes When a Valve Shuts, where we come out. 9 metros, each with its own page. 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Newer machines open and close their water valves quickly and often, and older plumbing with loose pipes or waterlogged air chambers cannot absorb the jolt. Arrestors at the connection usually quiet it. ### What is a water hammer arrestor? A short fitting with a sealed air cushion or a piston inside. Fitted between the valve and the supply line, it absorbs the pressure spike when the appliance's valve closes. ### Can water hammer damage the new appliance? Over time it can stress the inlet valve, the supply line and its joints, and the pipes in the walls. It is worth fixing early, especially with a dish care machine or laundry machine that fills many times a cycle. ### Does a braided supply line stop water hammer? It does not stop it, but a braided line of the right length with some slack passes on less of the jolt than a short, tight one. An arrestor is what actually absorbs the spike. --- **[Read on the site: Water Hammer After a Hookup: Banging Pipes When a Valve Shuts: Causes and Fixes](https://applianceinstallation.center/problems/water-hammer-after-hookup/)** **[Book a visit with ApplianceInstallation.center](https://applianceinstallation.center/schedule/)**