Ask The Brewmasters

Hello forumites, I'm looking for some help with some check valves.

We have been having issues with NPT check valves on our hot water mixing stations repeatedly failing and are seeing hot water get into the cold supply on several occasions.

Not only is this a safety issue, but we're also sometimes getting hot water into our rinser on the canning line too.

We quickly identify the culprit check valve and replace, but it's happening very often and I have tried multiple brands of in line check valves including Dixon. Most of the functioning ones are purchased through McMaster Carr https://www.mcmaster.com/1874N17 but even these have failed in under 1 year.

We're not seeing much mineral buildup that would indicate the seal to be compromised, but you can't really take them apart.

Our HLT supplies hot water to one cellar with 5 mixing stations using a pump on a pressure regulated VFD set to 50 psi. All mixing stations have check valves and then ball valves right before entry on both the hot and cold side. The issue only happens when both ball valves are open.

Could it be that the 50 psi is too high?

Are there other solutions or different designs that could work in this application?

I'd love to hear what others have seen or are using to remedy this problem.

Thanks!

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Jonathan Porter
Owner/Brewer
Smog City Brewing
Torrance, CA
porter@smogcitybrewing.com
310-980-8201
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Hi Jonathan,

Quick question, what is the line pressure of the cold water?

If it is less than 50 psi, the higher pressure hot water could be overcoming the backpressure of the cold water and potentially causing what I am picturing as your scenario.

Cheers,

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Nick Erickson
Technical Account Manager
AWC, Inc.
District St. Louis
nicholas.erickson@awc-inc.com
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Hey Nick,

Sorry this has taken me so long to respond to. I'm trying to understand exactly where the hot water is going on the cold side as we recently had the opposite issue happen in the brewhouse.

The cold/city water registers 64 psi and the hot water is maintained at 47 psi. In that case we shouldn't see flow from hot to cold due to a difference in pressure (under normal conditions).

Recently, the valves on a hot/cold mixing station was left open although the hose was not being used, we traced an inflow of cold water from that mixing station about 80 feet across the facility into the sparge manifold on the brewhouse. 

When we closed the ball valve, the temperature went right back to HLT temperature. In this case it was cold into the hot side of the piping.

My understanding of a check valve is that most are spring loaded and only flow in one direction. When flow in the opposite direction is initiated, the spring retracts and the seal shuts.

Even with a difference in pressure from hot to cold or vice versa, why would the check valves not close?

We have inspected a few of the check valves that failed for mineral buildup and worn or damaged seals and springs and they seem to be just fine. 

Any other suggestions?

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Jonathan Porter
Owner/Brewer
Smog City Brewing
Torrance, CA
porter@smogcitybrewing.com
310-980-8201
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Original Message:
Sent: 05-09-2024 17:50
From: Nicholas Erickson
Subject: Hot Water Check Valves

Hi Jonathan,

Quick question, what is the line pressure of the cold water?

If it is less than 50 psi, the higher pressure hot water could be overcoming the backpressure of the cold water and potentially causing what I am picturing as your scenario.

Cheers,

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Nick Erickson
Technical Account Manager
AWC, Inc.
District St. Louis
nicholas.erickson@awc-inc.com
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Hi Jonathan,

Our plumber warned us many years ago that two check valves on a mixing station can always have the potential to leak by if the piping downstream of the mixing station is kept pressurized.  He recommended two options, the first is to avoid having a valve downstream of the mixing station that can ever be shut so the space between check valves is always an open low pressure line.  The second option is to have a hot water and cold water valve before each check valve, and make sure your staff NEVER leaves both valves open when they are done using blended water.  

Our plumber explained that if the space between the check valves is pressurized with little to no flow coming from either side, some check valves can creep open slightly or even chatter with water pressure changes in the plant and allow small amounts of water to pass over to the side with less pressure, which is usually your cold water line.  If this happens enough you'll get that other water all the way back to the main city water supply.    Spring loaded check valves are less prone to do this flutter than a swing check valve but either valve has the potential to leak.   I've even had a working check valve that leaked by because of a very small strand of teflon thread tape that kept it from closing fully.    A regular check valve is not a fail safe device, that's why your municipality requires true backflow prevention valves at your city connection.  

The foolproof option would be to put in a really expensive Watts hot water rated backflow prevention valve on the hot side and regular backflow prevention valve on the cold water side.  That's going to get expensive, so managing a simple check valve mixing station and how the valves are used is your safest bet. 

As far as check valves, I've had good luck with just bronze swing check valves mounted horizontally, or if you go with a spring loaded check valve I would get a teflon ball check valve so you have no elastomer in the hot water side that will fail eventually from the heat.  Be sure to mount the spring loaded valves vertically so gravity doesn't cause issues on the valve closing cleanly or premature wear on the sliding shaft in it.    That being said, even with these two options, I've still had our mixing stations leak by if the mixing station wasn't used and shut off correctly.   

I hope that helps, cheers!   

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Curtis Holmes
Alaskan Brewing Co
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