Water hammer is a sharp bang or thud right after a valve closes quickly, often a washing machine, dishwasher or ice maker solenoid, or a single-lever faucet snapped shut. Before you buy anything, find out three things: which fixture triggers it, what your static water pressure is, and whether any accessible pipe is loose. Those answers tell you whether you need a pressure-reducing valve, pipe straps or a water hammer arrester.
Step 1: Find the trigger
Run each fixture and appliance one at a time and note which shutoff causes the bang.
- One fixture or appliance bangs: the fix is usually local, at that branch.
- Several fixtures bang: suspect high house pressure first.
- You hear rattling or see a pipe move: support the pipe first.
- Ticking or creaking while hot water runs, with no bang at shutoff: that is a different noise from water hammer, and an arrester won’t address it.
Step 2: Measure static pressure
Thread a pressure gauge onto a hose bibb or laundry faucet with nothing else running. Watts’ pressure-reducing valve guide notes that most plumbing codes require a pressure-reducing valve (PRV) on domestic systems where the main pressure exceeds 80 psi, and that higher pressures can damage pipes and fixtures. If your reading is above 80 psi, deal with pressure before adding local parts. If you already have a PRV and the pressure is still high, have it checked or adjusted.
A closed system also needs attention. If a PRV or backflow device keeps expanding hot water from flowing back to the main, ask a plumber whether you need thermal-expansion control at the water heater.
Step 3: Check pipe support
Look at exposed runs in the basement, crawlspace and laundry area. A pipe that shifts when you push it, or a strap that has come loose, can turn a small pressure pulse into a loud knock. Re-secure it with straps or hangers made for that pipe material.
Step 4: Add an arrester where the shock starts
If pressure is in range, the pipes are secure, and one fixture still bangs, an arrester at that fixture’s supply is the targeted fix. Match these:
- Connection and size: for example, Sioux Chief’s 652-A uses a 1/2-inch male thread connection and is listed for 1 to 11 fixture units. Other models use other sizes and connections.
- Hot and cold supplies: when a fast-closing valve, such as a washer’s, is fed by both lines, check whether the arrester maker calls for one on each.
- Placement: install it as close to the fast-closing valve as the maker’s placement guide calls for.
- Access: Sioux Chief says the 652-A can be installed at any angle without an access panel. Not every product can, so check before you close a wall.
Fix map
| What you find | First fix | What it won’t solve |
|---|---|---|
| Static pressure above 80 psi | Pressure-reducing valve | Loose pipes |
| Pipe moves or rattles | Straps, clamps or hangers | Pressure shock at a fast valve |
| One fixture bangs, pressure normal, pipes secure | Arrester at that fixture | Whole-house high pressure |
| Bangs at many fixtures with a PRV installed | PRV check or adjustment, then expansion control | A single local arrester |
When to call a plumber
Hire help for PRV installation or replacement, soldered or press connections, noise inside finished walls, corroded threaded joints, or pressure that climbs overnight on a closed system.
Related guides
FAQ
What pressure is too high for home plumbing?
Watts notes that most plumbing codes require a pressure-reducing valve when the incoming main pressure exceeds 80 psi. Check your local code, and measure static pressure with a gauge rather than guessing.
Do water hammer arresters fix loose pipes?
No. An arrester absorbs the pressure shock from a fast shutoff. Pipes that move or slap against framing need straps, clamps or hangers.
Do I need an arrester on every line?
No. Start with the fixture or appliance that triggers the bang. Add more only where the same shutoff pattern repeats.
Is a PRV enough by itself?
A PRV lowers supply pressure across the whole house. It doesn’t stop a loose pipe from moving, so pipe support still matters.