That bang in the wall when the washer finishes filling is water hammer. The machine's fill
valve snaps shut in a fraction of a second, the water column slams into it, and the
pressure spike thumps every loose pipe between the laundry room and the meter. It is loud,
it is annoying, and over years it works fittings loose.
The fix is cheaper than dinner. A washer-style water hammer arrestor is a small sealed
cushion that threads on between the shutoff valve and the supply hose, using the same
3/4-inch hose thread as the hose itself. No pipe cutting, no plumber. Screw on a pair,
run a fill cycle, and the bang is gone. Here are the two pairs worth buying and the
in-line fitting for hammer elsewhere in the house.
01 The picks
Two screw-on pairs for the washer, one fitting for everywhere else.
01 EFIELD S-241 Washer Arrestor Pair
Best for: most laundry rooms. The cheapest correct fix for a banging washer fill
Budget
This is the no-drama answer. The pair threads onto the hot and cold washer valves, the
swivel end means you tighten the nut without spinning the whole body, and the fill-cycle
bang stops that day. The rating on the listing is 250 PSI working pressure, which is far
past anything a house should ever see, and the body can sit horizontal or vertical, so it
does not care which way your valves point.
The honest knock is the paperwork. EFIELD is a budget parts brand, and the listing gives
you a pressure number and not much else. For a sealed fitting at this price that is a
trade most laundry rooms can live with. If you want the longer pedigree, spend up one
rung.
- Fittings3/4 in female swivel hose thread x 3/4 in male hose thread
- BodyLow lead brass with stainless steel
- Max working pressure250 PSI
- MountingHorizontal or vertical
- PackPair, one per valve
Skip it if: you want a name your plumber would recognize on sight. The Sioux Chief pair below is the same job from the brand in the plumbing aisle.
02 Sioux Chief 660-H Mini-Rester Pair
Best for: the buy-once pick from the brand the trades actually install
Mid-range
Sioux Chief is a plumbing-parts house out of Missouri, and the Mini-Rester is the arrestor
version of buying the part your plumber would have grabbed anyway. Same 3/4-inch swivel
hose fitting, same ten-minute install at the washer valves, brass and stainless in the
build, and a manufacturer that publishes actual installation guidance instead of a
marketplace bullet list.
That guidance includes the most useful sentence in the category: systems running above 60
PSI static pressure should have a pressure reducing valve upstream of the arrestor. Read
that as a hint, not fine print. If your house pressure is high, an arrestor muffles the
symptom while the pressure keeps beating on every valve and hose in the building,
including the washer hoses you least
want failing.
- Fittings3/4 in female swivel hose thread x 3/4 in male hose thread
- BodyBrass, stainless steel, and polypropylene
- Install pointWashing machine supply valves
- Pressure noteAbove 60 PSI static, maker calls for a PRV upstream
- PackPair, one per valve
Skip it if: the budget pair already solved it. Both do the same job at the same fitting; this one costs more for the brand and the spec sheet.
03 SharkBite Max Water Hammer Arrestor
Best for: banging at fixtures that have no hose thread, on accessible 3/4-inch pipe
Premium
Hammer is not only a laundry problem. Dishwashers, ice makers, and fast-closing
single-lever faucets slam valves too, and none of them give you a handy hose thread to
screw an arrestor onto. This SharkBite fitting solves that without soldering: it pushes
onto cut 3/4-inch PEX, copper, CPVC, PE-RT, or SDR-9 HDPE, works on wet lines, and can be
rotated or mounted in any orientation once seated.
Respect what push-to-connect means here. You are cutting pipe, deburring it, and trusting
an O-ring fitting inside your supply line, and getting it back off needs a disconnect
clip that does not come in the box. It is the right tool for hammer beyond the laundry
room, and overkill for hammer in it.
- ConnectionPush-to-connect, 3/4 in pipe
- Pipe typesPEX, copper, CPVC, PE-RT, SDR-9 HDPE
- Rated to200 PSI and 180 F
- MountingVertical or horizontal, body rotates
- RemovalDisconnect clip or tongs, sold separately
Skip it if: your only problem is the washer. The screw-on pairs above fix that without touching the pipe.
02 Why the pipes bang, and the free checks first
Two minutes of diagnosis before you buy anything.
Washing machines cause hammer because their fill valves are electric solenoids. A hand
faucet closes over a second or two; a solenoid slams in milliseconds. Water is heavy and
it was moving, so it piles into the closed valve and the shock wave has to go somewhere.
Pipes bang when the washing machine fills, stop banging when it agitates, and bang again
at the rinse fill. That rhythm is the diagnosis.
Before you order, run three free checks. First, look for loose pipe. A supply line that
crosses joists without straps will knock under even mild hammer, and ten cents of pipe
strap beats any arrestor. Second, try the old air-chamber reset: many houses have capped
vertical pipe stubs behind the valves that act as air cushions, and they slowly fill with
water until they do nothing. Shut off the main, open the highest and lowest faucets in
the house until everything drains, then close up and refill. If the bang disappears for
months and creeps back, you have air chambers, and a sealed arrestor pair is the
permanent version of that fix. Third, think about pressure. If faucets hiss and hoses
feel rock hard, high static pressure is making every slam worse, and the arrestor maker's
own 60 PSI guidance applies.
While you are behind the machine, look at the hoses you are about to unscrew. If they are
original rubber or past the five-year mark, this is the moment to swap in a
braided stainless pair,
and a leak detector on the floor
backs up whatever the hoses do next. Our picks here are judged on fittings, materials,
and published guidance rather than staged bench tests; the methodology lives at
how we test.
03 The ten-minute install
Same thread as a garden hose, and it behaves like one.
- Close both valves
Shut the hot and cold washer valves and start a fill cycle for a few seconds to bleed
the pressure out of the hoses. Keep a towel down; each hose holds about a cup.
- Unscrew the hoses from the valves
Counterclockwise, by hand if you are lucky, with channel locks if you are not. Steady
the valve body with your other hand so the pipe in the wall never takes the twist.
- Thread an arrestor onto each valve
The female swivel end goes on the valve. Hand-tight plus a small snug with pliers is
plenty; the washer inside the fitting does the sealing, not torque. No tape on hose
threads.
- Reconnect the hoses
The supply hose threads onto the arrestor's male end exactly as it sat on the valve.
Keep hot on hot and cold on cold, and let the hoses hang in a relaxed arc without
kinks.
- Open the valves and run a fill
Open both valves slowly, watch each new joint for a minute, then run a rinse-and-spin
cycle and listen for the moment the fill valve closes. Silence is the whole point. A
weep at a fitting means the washer is cocked: back it off, reseat, retighten.
04 Water hammer questions
Clunks, placement, and whether arrestors actually work.
Why does my washing machine clunk when filling with water?
The fill valve inside a washer is a solenoid, and it snaps shut in a fraction of a second. The water rushing toward it has momentum and nowhere to go, so it slams into the closed valve and sends a pressure spike back through the pipes. That spike is the clunk. A single thud right when the filling sound stops is the classic signature. Clunking during agitation or spin is mechanical and lives inside the machine, not the pipes.
Where does a water hammer arrestor go on a washing machine?
Between the shutoff valve and the supply hose. Unscrew the hose from the valve, thread the arrestor onto the valve, and thread the hose onto the arrestor. You need two, one for hot and one for cold, which is why the washer-style arrestors here sell in pairs. Both fittings are the same 3/4-inch hose thread as the hose itself.
Can you install a water hammer arrestor yourself?
The washer-valve style, absolutely. It threads on like a garden hose and the whole job is ten minutes with a towel and maybe a pair of pliers. The in-line style that tees into the pipe itself is a real plumbing task: it needs pipe access and a cut-in, so it lands in DIY territory only if you are already comfortable opening up supply lines.
How do you find the source of the water hammer?
Note what was running when the bang happened. A thud at the end of the washer fill is the washer valve. A bang when the dishwasher or ice maker cycles points there. A bang when you snap a single-lever faucet closed is that fixture. Hammer follows fast-closing valves, so the appliance that just stopped drawing water is almost always the culprit.
Do water hammer arrestors work?
For valve-slam hammer, yes. The arrestor gives the moving water a cushion to land on instead of a hard stop, and a screw-on pair at the washer valves usually kills the bang on the first fill cycle. If banging continues, look at house pressure and loose pipes. Sioux Chief's installation guidance calls for a pressure reducing valve when static pressure runs past 60 PSI, and a pipe that is not strapped down will knock against framing no matter what you screw onto the valve.
