Vacuum relief valve?

walker44 · 08-28-2009, 07:41 PM

I'm looking for a valve for an unusual circumstance. I have a large water tank that has a vent line running from the top. When the tank is overflowing, it uses the vent line to dispose of excess water. When the tank is drained from the bottom, it uses the vent line as an air vent.

If the vent line is blocked when the tank is draining, it will cause a vacuum that can damage the tank. I would like to install a valve on the vent line to allow emergency vacuum relief, but low pressure water still needs to flow freely in both directions past the vacuum relief valve without any leakage. I'm unable to add a valve directly to the tank and it needs to be installed on the vent line.

Is there a valve that will work and what kind is it. My vent line is 3/4, but I have size flexibility because of the tee. Will this fit my needs or will it leak?

http://www.plumbersurplus.com/Prod/Watts-Vacuum-Relief-Valve-N36-M1-3-4-(0138458)/5920/Cat/224?utm_medium=referral&utm_source=googlebase&cvsf a=63&cvsfe=2&cvsfp=5920

Hope my description is not too confusing. Thanks!

Just Bill · 08-29-2009, 07:25 AM

I think what you are describing is a T&P(temp/pressure) relief valve, although they are usually on the side of the tank. What was in your link is not the same thing. A pic of your existing valve would help us.

bob22 · 08-29-2009, 06:40 PM

Does the valve need to be automatic or would manual control work? What kind of material is the overflow made from? What diameter? How is it connected to the tank? Is there a threaded elbow? Picture would help.

JDC · 08-29-2009, 11:29 PM

That vacuum relief valve in the link should work just fine. You'll just need a 3/4" female adapter to screw it in to. We are required to use them on bottom fed water heaters.

walker44 · 08-30-2009, 04:05 PM

Thanks for the help!

Just bill: There is no existing valve because this is a DYI add on. The tank is a cold water storage tank, so temp and inside pressure is not an issue.

Bob22: The valve needs to be automatic, the overflow line is made out of 3/4 heavy duty plastic flex tubing. I was planning on inserting the valve in line with a barbed / threaded female tee.

JDC: Thanks, I was also thinking about using a standard check valve, but I think the Vacuum relief valve would work better. Do you know if the vacuum valve needs to remain vertical to work?

Plumber101 · 08-30-2009, 04:08 PM

Are you just concerned with debrie getting into the tank?

walker44 · 08-30-2009, 04:11 PM

I’m not concerned about debris. It’s not drinking water and the vent has a screen to stop larger debrie from entering the tank. I will try to post pictures.

Plumber101 · 08-30-2009, 05:04 PM

They what are you trying to accomplish that a simple 90 deg fitting won't do.

walker44 · 08-30-2009, 05:11 PM

Plumer101: I dont think I understand your question. a "90 deg fitting" ( i think you mean tee) would defaet the pupose of a vent line and allow water to pass where i dont want it. I need something that will allow air to pass into the system, but will not allow water to exit

walker44 · 08-30-2009, 05:31 PM

http://i709.photobucket.com/albums/w...r44/Vacuum.jpg

Plumber101 · 08-30-2009, 05:33 PM

I get it now. When the tank fills you don't want water to be released when it is full.