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Hot Liquor Tank pH post-treatment with sulphuric and hydrochloric acid blend

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  • Hot Liquor Tank pH post-treatment with sulphuric and hydrochloric acid blend

    We've recently started tracking pH more closely for our brewing liquor at different stages and vessels, in an attempt to understand a bit better how this all works and we have a few (for us) intriguing numbers that I hope some of you from the community might be able to shed some light on...

    We have our water analysed on a quarterly basis with fairly consistent pH coming in to our site.

    Water comes in at pH 7.5 to pH 8.0. We now measure raw liquor from our CLT just before knockout or when we're filling up the HLT. The numbers we're getting in the last month or so (since we started doing this) range from 7.10 to 7.94

    We've also been taking readings of the HLT post-treatment. And the numbers that got us thinking are related to one agent we add to the HLT - a blend of sulphuric (5 - 10%) and hydrochloric acid (1 - 5%) from one of our suppliers. The addition volume is 1.7 litres to a 5,000 litre-HLT.

    The addition process is straight-forward (the day before we brew) and takes into account full recirculation in the HLT before we take any readings the following day. The readings we got were roundabout pH 3.70 (which is the reason we decided to monitor this more closely).

    We contacted our supplier to check that this was normal as we didn't expect to see such a low reading to be frank. Their technical dept came back stating that the blend's target was to lower alkalinity levels, rather than adjusting pH (I get it that they're not one and the same, but I'd have guessed that lowering alkalinity levels would result in a lower pH too by default, but happy to be corrected on this).

    Anyway, brewing with this liquor resulted in mash start pH (15 minutes in), first and last runnings pH readings all consistently within our parameters, nothing out of the ordinary at all.

    Then out of the blue we had one brewday where the CLT readings were still within the range above (7.90), but the same liquor once in our HLT post-treatment was at pH 6.24. Same addition of our blend of acids. Readings throughout the brewday were still pretty much the same as before, nothing that stood out as unusual.

    On one hand we're happy with our readings throughout the brewday and throughout fermentation - no reason for concern here. On the other hand we felt a bit weird insomuch as we'd like to understand why we're seeing that 3.7 or thereabouts, which is a first for me. And finding out why we suddenly got such a different post-treatment reading would be nice too, moreso given that pH through the rest of the brewday was matching our expectations.

    We treat only the amount of liquor we use on that particular brewday - in the sense that we don't compound additions to the HLT. The left-over liquor is pumped out to be used in other areas of the brewery. We start with an empty HLT for a new brewday.

    The other addition on this water profile is made to the grist and before sparging, it's a blend of calcium sulphate and calcium chloride.

    These readings were done with more than one pH meter, and both are calibrated on a daily basis. The samples are allowed to reach ambient temps before us taking readings.

    Any pointers would be greatly appreciated.

  • #2
    If you are using stainless steel tanks, stop using hydrochloric acid unless you want to risk extensive and destructive corrosion due to the chlorine ions attacking the chromium dioxide layer. I suggest you use lactic acid instead of hydrochloric if you need to limit the amount of calcium sulphate ions. I also suggest that if your water contains bicarbonate in particular, that you treat the CLT. This way you are far less likely to foul the wort chiller with calcium carbonate deposits, which will inhibit heat transfer, and require you to acid clean the water side of the chiller periodically.

    You can get proportional dosing pumps which do not require separate (electrical) power supplies. Have a look at for examples. Use one of these types of pump to proportionally dose your acids on the CLT top up line.


    • #3
      Thanks for the prompt reply... We don't have a particularly bad problem with calcium sulphate with our liquor, but we're about to send our water for analysis again soon - the lab that does it for us is the same supplier fo the acid blend, so we'll take the opportunity to make further enquiries re this blend, let's see what they come up with.

      And yeah, we use a dosatron in another area of the brewery so we're well familiar with their products. The CLT dosing is an interesting idea.



      • #4
        I agree what Dick is saying concerning the hydrochloric acid. Try to avoid - not always possible - any chlorinated product. These products, if not very well rinsed out, can damage your stainless steel by pitting.
        Also, if you want to do a pH adjustment for your mash, I recommend either food grade lactic acid or food grade phosphoric acid. The two acids (sulfuric and hydrochloric acid) you mentioned are not ideal for pH adjustment in the mash.
        Why you had suddenly such a significant pH drop to 3.70 is indeed interesting. Maybe the mixing was not sufficient. Keep in mind sulfuric acid has a much higher density as water. That could be one cause. Depending on what the water contains there could be a higher or lower buffering capacity (alkalinity). Also, the mash can have different buffering capacities. Adjusting the pH shortly after mashing in is a more precise step. Take a small mash sample strain it to remove all solids and put 100 mL on a stir plate with the pH probe in the sample. Titrate with the acid used to adjust the pH and once reach the target pH upscale the used volume to the total mash amount. once added and thoroughly mixed control again the mash pH.
        The Dosatron pump is a nice and pretty good dosing pump. I would still check the pH of the final batch in the HLT to ensure the dosing is correct.
        Zee Loeffler
        888-484-6248 (US & Canada only)


        • #5
          Apologies for the late reply, we're brewing today and I wanted to wait for our pH readings first just to see what we're getting...

          CLT (raw): 7.8 (expected)
          HLT (treated): 5.0 (unexpected)
          Mash (15 minutes in): 5.7 (slighty higher than usual)
          First runnings: 5.44 (expected)

          The HLT was treated wth that acid blend today.

          We do treat our liquor differently for other recipes, and we do use lactic acid to lower the pH for our pilsner, with great results

          And thanks Oliver for the pointers - I think the first step now will be a fresh water analysis followed by a discussion with their lab team re whether we can ditch the blend, and maybe go sulfuric acid and lactic acid only, but to be frank I wouldn't know what kind of possible scenarios that would bring us. As the numbers today show, we're close to or on point for every reading, apart from the HLT, which fluctuates wildly, maybe due to this density of the H2SO4... even though we can't really see how much more recirc we could give the HLT...

          Anyway, cheers for all the info again!