I'm not a plumber though I do all my own work.
Ideally, every water outlet should have a hammer trap - one for cold, one
for hot. Most simply, a hammer trap is teed into the supply line as close
as possible to the outlet. A trap includes at least a foot of pipe of the
same size as the run (or even better a size or two larger), oriented
vertically up from the tee, with a cap at the top.
If you don't have hammer traps you will likely get water hammer. Hammer
traps do tend to fill up with water as the air entrapped in them gradually
becomes absorbed into the water. If at all possible, try do thoroughly
drain the house at least every year, making sure to open all faucets etc. to
drain all water from the traps and fill them with air.
It occurs to me that since you note that the problem happens when the supply
water is colder, you may have one or more traps that allow more interface
between the water and the trapped air - and cold water holds more air than
warm water does, hence it would happen more quickly when supply water is
colder. But that seems more theoretical and should only change the speed of
air absorption a small amount.
Karl
-----Original Message-----
From: Larry Spector
Subject: [Bulk] Re: [Shop-talk] Seasonal water hammer?
Thanks for the feedback.
There are small "preventers" on the back of my clothes washer, but there's
not much volume there. I've tried draining the whole house a couple of
times, to try and empty out any water that may have collected. That tends to
work for a week or so, but it doesn't last.
I was thinking of adding an expansion tank near the water inlet, something
like this:
http://www.homedepot.com/p/Watts-8-5-in-W-x-11-5-in-D-x-8-5-in-H-Pre-Pressur
ized-Steel-Water-Expansion-Tank-DET-5/100677607
I believe that it might be easier to do this, than to add vertical pipes in
the space I have access to.
-Larry
On Wed, Nov 5, 2014 at 1:33 PM, Eric J Russell <ejrussell@mebtel.net> wrote:
> Is there a water hammer preventer in the system? (I don't know if that
> is the real name - usually a capped off section of vertical pipe, the
> intention is for that vertical piece to be filled with air and act as
> damper for sudden changes in water pressure.)
>
> If so, the cold weather would likely reduce the volume of air in the
> water hammer preventer, lessening the dampening effect. Draining the
> water pipes might let it get refilled with air and return the preventer to
full effect.
> Or a larger vertical pipe (longer or larger diameter) might fix it.
>
> Eric Russell
> Mebane, NC
>
> ----- Original Message ----- From: "Larry Spector"
> <lspector@gmail.com>
> To: "shop-talk" <shop-talk@autox.team.net>
> Sent: Wednesday, November 05, 2014 12:50 PM
> Subject: [Shop-talk] Seasonal water hammer?
>
>
>
> I've got an odd problem, and it's been going on for a couple of years
now.
>> Every fall, when the cold water supply (county water) starts getting
>> even colder, I get water hammer. I can usually get it to go away by
>> turning off the tap and turning it back on slowly, but it's a pain to
deal with.
>>
>> Any idea what may be causing it and what can be done to alleviate it?
>>
>> Thanks,
>> Larry
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