Build a Spunding Valve! – How and Why

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A Spunding Valve allows you to maintain a set pressure.  If pressure in the vessel exceeds the set point, it is expelled.  It generally consists of an adjustable PRV valve, a tee, a gauge and a way to connect to your keg.

Homebrewing Applications of a Spunding Valve

  1. Pressurized fermentation.  Ferment in a 5 or 10 gallon corny keg and use your Spunding Valve instead of an airlock.  This allows you to ferment at your desired pressure.
  2. Dry hop under pressure.  This allows you to dry hop earlier while reducing oxygenation.  Active yeast are more likely to metabolize oxygen that’s introduced during dry hopping during active fermentation.  Since CO2 is not exiting beer as vigorously under pressure, wanted compounds, flavors and aromas are more likely to stay in your beer under pressure.
  3. Naturally and accurately carbonate beer right in the keg.
  4. An airlock replacement.  Keep the valve wide open for non-pressurized fermentations.  Only do this if you have plenty of head space.  This wouldn’t make a great blow off tube.
  5. Keg to keg transfers.  Use the Spunding Valve to allow excess gas to exit the receiving keg as you transfer under pressure.  Helps you achieve a slow, controlled and pressurized transfer.
  6. Fix over-carbonated beers.
  7. Test for keg leaks.  Pressurize your keg to serving pressure.  Put the Spunding Valve on (with the pressure set well above your serving PSI) and note the reading.  The gauge should remain steady.  If pressure drops, you know you have a keg leak.  It’s worth noting that this checks the entire keg including gas body o-ring.  That spot is hard to check and other way as it’s only in function when the gas QD is on.  When the gas QD is on… it’s difficult to spray and check for bubbles underneath the gas QD.  Thanks to Scott Janish for this tip!
  8. As an airlock for long term aging of beers.  Airlocks can run dry over time.  A Spunding Valve will not.

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This is a 2.5 gallon batch of beer that I fermented and naturally carbonated all in a 5 gallon keg.  This is a carbonated beer that I poured immediately after it was transferred into a serving keg.

Carbonating with a Spunding Valve

Carbonation directly in your keg allows you to naturally carbonate your beer (saving CO2 and $) while maintaining reasonably tight control on carbonation levels.  This could be done by adding priming sugar, capping fermentation prior to the completion of fermentation or more traditional krausening (adding wort back to the fermenter) methods.

Basic Steps for Carbonating in a Keg Using a Spunding Valve:

  • Prime the keg with your choice of priming sugar or wort (or start this process late in fermentation when some fermentable sugars remain)
  • Determine your desired pressure based on temperature and desired carbonation using a carbonation chart.  See: Balancing Your Draft System for a carbonation chart.
  • Pressurize the keg to just over your desired final pressure.
  • Attach the Spunding Valve
  • Dial down the pressure until you achieve your desired pressure
  • Wait.  As the remaining simple sugars are fermented, carbonation occurs and excess CO2 will be expelled from the spunding valve giving you just the right amount of carbonation.  I give it a couple days after reaching target pressure.  If you’re less sure how much fermentable sugar remained, I would suggest giving it a few days longer.
  • Chill your keg, allowing your beer to absorb head space CO2 and reach equilibrium.

Fix Over-Carbonated Beers

Use the same general process as for carbonation (skipping the addition of fermentable sugar).  Use a carbonation chart to determine proper pressure for the temperature the keg is at.  See: Balancing Your Draft System for a carbonation chart.  The Spunding Valve allows excess pressure to vent until the new carbonation level is achieved.  You can agitate the keg to fix carbonation more quickly.

Building A Spunding Valve

Note: Product pages may display other size variations of the fittings used here.  If a particular size is out of stock, sometimes suppliers link to another size.  All thread sizes for this build, both NPT and flare, are 1/4″.  If you want to replicate this build, pay special attention to the fitting sizes that are used and double check to make sure you’re purchasing the correct size fittings. 

cln_img_9894This valve [Control Devices CR Series Brass Pressure Relief Valve, 0-100 psi Adjustable Pressure Range, 1/4″ Male NPT] is the heart of this Spunding Valve build.  It is essentially a manually adjustable pressure relief valve.  This one is adjustable from 0 to 100 PSI.  There is no homebrewing-related situation I’m aware of that would have you at 100 PSI.  Generally you’d be at or below 30 PSI.  As always, you’ll want to ensure that all components in your system (kegs, tubing, etc) are rated for your desired pressure.  Also, always read and follow manufacturer’s instructions and guidelines.

61uDeVq1w5L._SL1315_This build constitutes the second version of this valve for me.  My first build had a 30 PSI gauge.  That’s good for almost every situation.  With this update I wanted the ability to go to a little higher pressure if needed.  I used a Zenport DPG60 Gauge.  It reads 0 to 60 PSI.81uS3xkiWIL._SL1500_This stainless 1/4″ tee fitting connects the relief valve, pressure gauge and a final connection fitting together.  Practically speaking any properly rated 1/4″ NPT threaded tee fitting should work.cln_img_9897The tee fitting, gauge and valve together.  The gauge required valve sealant tape, the relief valve came with some sort of thread sealant.

The only thing that remains is choosing how the assembly will connect to your serving or fermenting keg.  These are grouped into general connection styles.  Some styles have similar fittings that accomplish the same thing.  Additional fitting options for each build can be found in the complete parts list toward the end of this post.  When I’ve tried a fitting, I’ve included a photo.

Style 1: FFL (Female Flare) connection ready to connect to a pin or ball lock QD.  This version consists of Gas ball lock QD (it could just as well be a pin lock QD) – this fitting [1/4″ NPT Male x 1/4″ JIC Size] –  Stainless Tee – pressure gauge and this valve [Control Devices CR Series Brass Pressure Relief Valve, 0-100 psi Adjustable Pressure Range, 1/4″ Male NPT].  Valve Sealant tape goes on the first fitting and the pressure gauge.

spunding valve buildStyle 1 in action

Style 1 Variation: Using a brass fitting – LASCO 17-6783 1/4-Inch Female Flare by 1/4-Inch Male Pipe Thread Brass Adapter

cln_img_0276Style 2 [as of the most recent update to this post, this fitting is not available in the size I used for this build, pay close attention to the note about thread size that follows]: MFL (Male Flare) connection ready to connect to a flare 1/4″ swivel nut.  This version consists of  this fitting [1/4″ NPT Male x 1/4″ JIC Male] Note: This product page may show multiple size options.  Also availability of the correct size can be an issue.  Make sure you order the correct size or see alternate options at the bottom of this post. –  Stainless Tee – pressure gauge and this valve [Control Devices CR Series Brass Pressure Relief Valve, 0-100 psi Adjustable Pressure Range, 1/4″ Male NPT].  Valve Sealant tape goes on the first fitting and the pressure gauge.  The 1/4″ MFL can connects to 1/4″ FFL female flare of your choice.cln_img_0281Style 2 with tubingcln_img_0282This version is nice if you’re tight on space.  You can coil it up on top of a keg or set it off to the side.

cln_img_0287Style 3: 1/4″ barb – Ready for whatever 1/4″ ID tubing you’d like to use.  This version consists of this fitting [1/4″ Hose Barb 1/4″ Male NPT] –  Stainless Tee – pressure gauge and this valve [Control Devices CR Series Brass Pressure Relief Valve, 0-100 psi Adjustable Pressure Range, 1/4″ Male NPT].  Valve Sealant tape goes on the first fitting and the pressure gauge.

Style 3 Variation: Using a brass barb – Anderson Metals 57001 Brass Hose Fitting, Adapter, 1/4″ Barb x 1/4″ NPT Male Pipe

Style 3 Variation: Using a brass barb – Anderson Metals 57001 Brass Hose Fitting, Adapter, 1/4″ Barb x 1/4″ NPT Male Pipe and brass tee – Anderson Metals 56101 Brass Pipe Fitting, Barstock Tee, 1/4″ x 1/4″ x 1/4″ NPT Female Pipe – thank you to /u/workaccount32 on reddit for this photo

Style 4 : This build uses a cross fitting instead of tee fitting.  The additional leg has a ball valve [1/4″ Stainless Steel (316) Mini Ball Valve – FxM NPT] on it.  My thinking on this was to give you the option to use one Spunding Valve on multiple kegs.  This could be for any of the functions mentioned above.  Pick the connectors you want for your intended purpose.  One idea – ferment one beer under pressure and use that pressure to force carbonate another beer to save CO2.

Spunding Valve Tips

  1. Check for leaks.  If you’re using a version that has a QD installed in some form or fashion, you can pressurize it on a keg and then take it off.  There will be a small drop when you take it off, but the pressure should remain steady after that.  If it’s going down, make sure everything is tight.  If you don’t have a QD… spray with Star San or soapy water until you are leak free.
  2. When setting desired pressure… start high and work your way down.  As the valve gets close to where it is going to eventually settle, it slows down the release of gas.  Working your way slowly down, helps you hit your desired pressure without passing it (going too low).

cln_img_9929Here I’m dialing in my desired pressure.  Also pictured: Thermapen Mk4 [Review].

Spunding Build Parts List

Note: Product pages may display other size variations of the fittings used here.  If a particular size is out of stock, sometimes suppliers link to another size.  All thread sizes for this build, both NPT and flare, are 1/4″.  If you want to replicate this build, pay special attention to the fitting sizes that are used and double check to make sure you’re purchasing the correct size fittings.

Build Components:

Keg Fitting Options – How do you want your Spunding Valve to connect to kegs or fermenter?  I’ve tried many of these fittings myself.  For fittings I’ve tried, I include a link to a photo

Style 1 – Female Flare, Connect to Pin or Ball Lock QD

Style 2 – Male, Flare, Connect to tubing via Swivel Fittings

Style 3 – 1/4″ Barb, use tubing clamp to connect directly to tubing

 Cheapest Option:
Generally speaking, the brass variations of these fittings are probably going to be the most economical route to go.  This is a general statement and may not always be the case.  Check product pages for current prices and availability.

Thank you to /u/workaccount32 on reddit for this photo

Search: As mentioned previously, availability of fittings in the proper sizes can be an issue.  This has proven especially true for the keg fitting options piece.  The two thread types for that piece in this build are 1/4″ npt and 1/4″ SAE JIC.  This Amazon Search may be helpful in finding compatible fittings for the build you’d like to complete.  Note: that search may very well return fittings that are not helpful for this project.  Pay attention to thread size, material and fitting gender.  If you find a great fitting that isn’t listed here, Submit a Tip and let us know about it.

Gas Keg Disconnects:

Brew Hardware Fittings – similar, but not identical to what I used for the builds found in this post.

Ready Made Spunding Valve: A couple ready made options are now available

Always make sure the parts you use are compatible and are rated for your intended application.  Contact manufacturers with questions about suitability or application.

Pinned: Black Friday Roundup! | Amazon’s Black Friday Deals Weeksubmit a tip

Recent Great Deals [view more]:

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25 thoughts on “Build a Spunding Valve! – How and Why

  1. Bill

    When fermenting under pressure, wouldn’t the spunding valve act as a blow off as the gas is released, damaging it?

    Reply
    1. admin Post author

      Not sure I understand what you’re saying. The adjustable PRV vents pressure in excess of the set point.

      Reply
      1. Bill

        Yes, I wasn’t very clear. I’m not worried about the gas doing the damage, but the krausen (?) would cause problems, wouldn’t it?

        Reply
        1. admin Post author

          Gotcha, Yes krausen could be an issue. I think that pressure fermentations have less krausen in general, but you would want to make sure there’s enough head space so krausen doesn’t come out the spunding valve. Another comment on here details a method to clean the valve. I haven’t tried that out, but I think the best thing to do make sure you have appropriate head space so this doesn’t happen.

          Reply
          1. Nathan

            I am pretty sure it depends on how you do it. From what I have been told, you want to transfer it into your final keg with around 4 points left which should be enough fermentation left with the yeast to create around 2.4 volumes of c02 and shouldn’t mess with the spunding valve as long as you are leaving normal head space in the keg. Granted this is purely natural carbonation using the yeast to create and carbonate the beer for you. No adding in priming sugar or anything. More or less the way that German breweries will do it along with doing LODO as far as brewing. I havent done this method yet but plan on doing it my next batch if I can get everything done in time. This guy is going from finished wort to fully naturally carbonated lager beers in 7 days.

  2. Curt

    If you are using Option 1 to transfer beer to a keg and you overfill the keg, what prevents beer from coming out the spunding valve and worse into the pressure gauge. Can the spunding valve be cleaned and sanitized easily? Seems like Option 2 with the hose might have an advantage for this purpose.

    Reply
    1. admin Post author

      Great question! The answer is… nothing. You’d want to be careful not to do that. You could clean out most of the fittings, but probably not the gauge and maybe not the adjustable pressure relief valve. You’re right that option 2 would have an advantage in this regard as you’d be able to see the beer coming.

      Reply
      1. zak

        Actually, there is a way to clean the valve! Fill a clean keg with a gallon of distilled water, pressurize it through the gas line, then hook up the spunding valve to the liquid line. Dial the valve down to zero and water will shoot out, so you might want to do this in a bathroom/outside. Let the gallon of distilled water run through, and then run co2 through the valve to dry it. Cheers.

        Reply
  3. Konrad

    With Option 1, I was losing approximately 1 PSI per day, until I forced teflon tape into the swivel joint of the 1/4″ NPT Male x 1/4″ JIC Female fitting. Now it’s holding steady.

    Reply
  4. Jake

    The link for the 1/4″ NPT male x 1/4″ JIC flare isn’t available on the link you provided

    Smallest size I saw was 1/2″…

    Know of any other sources to buy this piece? I would prefer to stick with the smaller footprint of “option 1”. Thanks!

    Reply
    1. admin Post author

      Hey Jake. Those links go to the general part page and then you select your size from there. I’ve tried to note that throughout the post. There have been availability problems for a while. I’m looking for alternate sources/parts but haven’t come up with anything yet.

      Reply
  5. Will Fisher

    Hi, amazing article thank you. I really need this, one very important question tho.

    If I set my desired pressure to 20 psi, when the tank reaches more than 20psi it will open and release pressure. Does it close again at 20psi to maintain that desired pressure? Or does it just release all the pressure in the tank so you have to start building pressure again from zero?

    Reply
    1. Roman Goyenko

      The valve is open if pressure is over 20 psi and closed if under 20. So it will build up to 20 and then maintain it.

      Reply
      1. admin Post author

        For clarification, I don’t believe that you can reliably determine pressure using any of the markings on the adjustable PRV valve. The gauge, in my opinion, is a necessary component.

        Reply
  6. Scott

    I purchased the valve and have a question when using. The markings for the valve readings aren’t very accurate. The gauge reads 10 psi for example and the valve is set to almost 30 to keep the gauge stable at 10 psi. Is this your experience?

    Reply
    1. admin Post author

      No, that’s not my experience. The gauge reads a couple PSI off of what my regulator says, but I’m not sure if it’s wrong or if the regulator is wrong. In any case, they are close.

      Reply
  7. Roy

    Great idea to have the Schraeder valve on there as well. You could use a regular air hand pump to move cleaner and santizer through kegs and save on CO2.

    Reply
  8. Brandon

    I use a variation of option 2 on a conical for co2 transfer. If you use a cross instead of a tee you can throw a triclamp on the additional side or cap it off as needed for testing the guage (or fermenting in a keg). The MFL side is used with a gas line to transfer the beer in my case. That same line also can thread onto a beer gun, which is one advantage to using MFL’s. I didn’t think about it until reading this article, but I can cap that MFL off to use as a spund. The conical can’t hold the pressure like a keg can, but I can get a jump on it a save a couple days off the carbonation process by setting at 10psi or so. I’ll have to try it next time. Thank you.

    Reply
  9. Perzell Brewing

    A possible solution for the flare fitting would be this fitting I know it is brass, but it is a check valve (to ensure you don’t get any stuff in your pressure relief valve) and it can fit directly on your quick disconnect.

    Reply
    1. Perzell Brewing

      After reading more about the check valve I mentioned, I don’t know if it would be a good buy for Spunding Valve because it won’t let air flow opposite direction. The SS fitting in this article is sold out. Brass alternatives:

      Option 1
      Option 2

      Reply
  10. Dave

    Nice write up. I just kegged my first beer. Is there any reason to use the female over the male flare fitting? or vice a versa.

    Reply
    1. admin Post author

      Hey Dave! – I suppose it comes down to how and where you’re going to use it. I like the “option 1” build the best. I like being able to attach this right on a keg with no tubing. It’s a neat, clean setup. Having said that I think the second option is good too. Practically speaking, they all do the same thing.

      Reply

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