Subject: Re: [Shop-talk] Seasonal water hammer?

From: "Eric J Russell" <[email-masked]>
Date: Wed, 5 Nov 2014 13:33:15 -0500

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" <[email-masked]>
To: "shop-talk" <[email-masked]>
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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[email-masked]
Archive: http://www.team.net/archive

---

From: Larry Spector <[email-masked]>
Date: Wed, 5 Nov 2014 14:46:26 -0500

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-Pressurized-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 <[email-masked]> wrote:

> 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.)
>
> ----- Original Message ----- From: "Larry Spector" <[email-masked]>

[email-masked]

---

From: "Karl Vacek" <[email-masked]>
Date: Wed, 5 Nov 2014 14:52:16 -0600

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

-Larry

On Wed, Nov 5, 2014 at 1:33 PM, Eric J Russell <[email-masked]> 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 
> 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.
>> 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.

[email-masked]
Archive: http://www.team.net/archive
http://autox.team.net/mailman/options/shop-talk/[email-masked]
_______________________________________________

[email-masked]

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From: "Pat Horne" <[email-masked]>
Date: Wed, 5 Nov 2014 16:07:22 -0600

Larry,

I've had this kind of problem on taps that we don't use often. Turns out
that the problem was that the packing nut on the tap was loose, allowing the
valve stem to move a bit, affecting the water flow through the valve. I've
also heard that a loose faucet washer can cause the same thing. Do all your
taps do this, or just one or two? If you turn on the taps for your washing
machine and run the washer, is there water hammer when the washer shuts the
water off? If not, then it is probably not a water hammer, but modulation of
the water flow such as I described to start with.

Peace,
Pat
deal with.

[email-masked]

[email-masked]

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From: David Scheidt <[email-masked]>
Date: Thu, 6 Nov 2014 13:33:24 -0600

> On Nov 5, 2014, at 14:52, "Karl Vacek" <[email-masked]> wrote:
>
> becomes absorbed into the water.

If you have hammer traps, and you don't have water hammer, you
wouldn't have water hammer if you didn't have them.

Air chamber hammer traps simply don't work. They're full of water, and
not air, in a few days to a few weeks, depending on the usage, the
water pressure, and pipe sizes.  Once they're full of water, their
only purpose is to grow bacteria.  Even when they're newly drained,
they're invariably too small.

Water hammer is prevented by using proper pipe design to keep flow
rates below about 5 feet per second, and by keeping branches as short
as possible.  If you meed an arrestor, use a mechanical one sized for
the job.
_______________________________________________

[email-masked]