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hard knock in water line when valves switch

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James

Starting Member

Posts: 1

1

Friday, September 19th 2008, 5:52pm

hard knock in water line when valves switch

How do I cure the problem of the hard knock in the water line when each valve switches zones?

Lowvolumejeff

Advanced Member

Posts: 91

Location: Seattle Area

2

Friday, September 19th 2008, 9:56pm

Sounds like the dreaded Water Hammer

James, sounds like you ae experiencing Water Hammer. Several causes, but sounds like your is due to the valve closing to quickly, or more corectly, having to great a velocity thru it when the last bit of the opening is closing. It is caused by a shock wave back into the main line in this case. Usual cause is too much velocity in the pipes (greater than 5 fps) and is best remedied by using larger pipes. Sometimes, changing valves can help. Please post more information about your system, size and type of pipes, type of valves, number and type of heads on a zone (or ideally the GPM the zone is using), so our answers will better suit your needs.



Another cause can be water rushing into empty (air filled) pipes. This can be remenied in diferent ways, and although I have never tried it, air relief valves have been suggested.

Good luck. Jeff

Lowvolumejeff

Advanced Member

Posts: 91

Location: Seattle Area

3

Friday, September 19th 2008, 10:02pm

Water Hammer = BAD

Sorry, but I forgo to mention that water hammer is bad. It will literally knock your system apart if bad enough, and most probably lead to a prmature failure of one or more parts.

Sorry

drpete

Moderator

Posts: 44

4

Friday, September 26th 2008, 12:18pm

RE: Water Hammer = BAD

Quoted from "Lowvolumejeff"

Sorry, but I forgo to mention that water hammer is bad. It will literally knock your system apart if bad enough, and most probably lead to a prmature failure of one or more parts.

Sorry
Agreed. you must fix the problem. Just imagine it happens while your away for a weekend and breaks a pipe in your basement. Water running for 48hrs in basement= BAD

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