OC Laboratory

2025 Laboratory Event Description  *UPDATED 3/13/2025

2025 Laboratory Judging Sheets:  Head Judge; Judge 2; Judge 3; Judge 4   *NEW 2/27/25
The judging sheets are provided primarily for event coordinators and judges information only. They are not part of the procedures or the rules of the event. They are for reference only and do not govern; the event descriptions govern. They are updated periodically and are subject to change at any time, without notice. They may not be used in any form of protest or question. There may be actions that are penalties that are not explicitly listed as an example on the penalty sheet.

US - LABTEST
Canada – LABTESTCA

Table Layout 
Photo is two set ups back to back. WEFTEC  setup will be tables in a row – left to right – at an angle.  Like an arrowhead.

We will using the lab tables that we have had for the past lab events.  There will be 2 tables so each test can performed on its own table with the spec on 1 of the table to perform the readings. The table dimensions are 96”L x 30”W x 36”H.

The trays will be on the opposite table from the where the Hach DR3900 spec is located.

The 2 4L bottles will be dumped into the 10L carboy for ease of use.

There is no kit from Hach but they have provided these discount codes that can be used every time you order it gives you 20% off.

US - LABTEST

Canada – LABTESTCA

Yes there will be a new table layout coming soon.

1.  Will the DR3900 be turned on during setup? 

2.  Will the tap water be in a carboy the same as the DI water? 

3.  Will there be a 500 ml wash bottle with tap water to enable rinsing or will it be from the 4l container or carboy? 

1.  There will be 2 carboys

2.  Yes you are correct the unknow will be one of the 10, 15, 20 or 30 and the calculated unknown will be the unknown multiplied by 5.

1.  Yes they will be filled before by the lab coordinators

2.  The beaker containing the what you poured out of the ampule is where you pull for the second round of chlorine testing.

How close do we have to get to the nominal concentrations to get bonus time? 

1. For the 2ppm phosphate standard, the procedure indicates rinsing the 100mL volumetric flask and 100mL graduated cylinder 3x with DI, then rinsing 1x with the unknown standard. Wouldn't rinsing last with this standard potentially introduce contamination and an artificially inflated dilution concentration?

2. When rinsing the Cl2 glassware, the procedure indicates rinsing 3x with tap water (from a 250mL beaker) and 3x with DI for everything used in the event.   This equates to around 48 rinses per run before any dilutions can be created. Is it possible we could investigate removing the tap water rinse?

3. When rinsing the Cl2 sample cells after the first set of readings, does the sample cell need to be rinsed with tap water 3x and DI water 3x as previously stated? If not, how many times does it need to be rinsed with DI water? 

4. Will we be required to label any of the TNT or Cl2 sample vials? 

5. Will we be required to label the 100mL volumetric flasks? 

1.  This is standard lab practice to rinse with the standard. It will not artificially inflate the dilution concentration.

2.  The procedure as written will be followed.  If after going through competitions we feel things need changed, we will do so.

3.  The Cl2 sample cells needs to be rinsed in between each new sample that is being poured into it. The cell should be rinsed 3x with DI water in between each new sample being poured into the Cl2 sample cell.

4.  No.

5.  Yes

For phosphate sample with unknown concentration, do we need to rinse the STD beaker with DI water, the dilution or both? Or do we not rinse at all.  

See step 1 of the Phosphate sample with unknown concentration in the procedure. *UPDATED

1.  Labeling step 5: Does the DI beaker need to be rinsed prior to adding DI water to it? 

2.  Phosphate sample with unknown concentration step 1e: Does the "STD" labeled beaker need to be rinsed prior to transferring the solution to it? If so, DI rinse and/or solution rinse? 

3.  Phosphate Standard Solution step 3 b: Does the solution B need to mixed 5 times like it was for the initial sample with unknown concentration? 

1.  Yes rinse 3 times with DI water

2.Yes it needs rinsed with solution once before filling with the solution.

3.  Yes it needs mixed 5 times inverted at a 90 degree angle.

In one of the previous questions it is mentioned that we need to label the 100ml volumetric flask, what do they need to be labeled as? 

What will the volumetric flasks be labeled? 

1.  Can we label the beakers during set up? 

2.  Can we unscrew phosphorous test tubes during set up? 

What exactly can't we do in setup? Setup instructions are not listed in the procedure. Ex. remove powder pillows, pipette tips, test vials, etc. from their respective bags/boxes. 

The procedure has been updated to include setup instructions.

1. Since there will be two carboys on the table, will the two 4L bottles of deionized water and the one 4L bottle of tap water still remain on the table? 

2. For clarification, this question was previously answered differently twice: Should we rinse the STD-labeled beaker with the unknown phosphate sample, deionized water, or both?

3. Is there an update on the table layout, and will the tables be the same size? 

Question #1 - Do all glassware used for the stock solution and standard solutions need to be dried after being rinsed with D.I. water? 

Question #2 - We know that the 2025 lab event will include two chemical analyses, Phosphate and Total residual chlorine. Both TDS and TSS analyses no longer part of this event? Can you clarify why a 50g calibration mass, and an analytical balance are on the material list? 

1.  Will the CL2 ampules be refrigerated or room temperature? 

2.  Will the foam container for the ampules be sealed or unsealed? 

3.  Will each team get fresh Solution B for each Lab run? 

The programs will not be stored in Favorites it will need to be selected via number from the index.

The procedure will be updated in the next week.

The lab event will be with the DR3900 for at least the next 4 years.

1.  The procedure has been updated to show 3 cells.

2.  There are no rules stating you can’t touch the tubes in the test tube rack after you use the dosicap. Mixing the tubes 5 times should be plenty to mix.

Rinsing can come from either the carboy or the tap beaker.

Please refer to Phosphate Sample with unknown concentration step 1.  You always measure 20 mls of the unknown into the graduated cylinder then bring to volume. The 2mls you take from the graduated cylinder and put into the tnt tubes will give you a reading that will then be multiplied by 5 to give you what the unknown true value is. You don’t use the C1V1=C2V2 for this step.

They determined that the unknown is 30 mg/L, to prepare a 2 mg/L standard, using C1V1 = C2V2: (30 ppm)(x) = (2 ppm)(100 mL).

Solve for x (V1) = 6.67 mL
C1 = 30 mg/L
V1 = 6.67 mL
C2 = 2 mg/L
V2 = 100 mL

The operator will now use the variable pipets to add 6.67 mLs of the 30 mg/L add to the volumetric flask and bring the volume to 100 mLs.

They determined that the unknown is 30 mg/L, to prepare a 2 mg/L standard, using C1V1 = C2V2: (30 ppm)(x) = (2 ppm)(100 mL).

Solve for x (V1) = 6.67 mL
C1 = 30 mg/L
V1 = 6.67 mL
C2 = 2 mg/L
V2 = 100 mL

The operator will now use the variable pipets to add 6.67 mLs of the 30 mg/L add to the volumetric flask and bring the volume to 100 mLs.

They determined that the unknown is 30 mg/L, to prepare a 2 mg/L standard, using C1V1 = C2V2: (30 ppm)(x) = (2 ppm)(100 mL).

Solve for x (V1) = 6.67 mL
C1 = 30 mg/L
V1 = 6.67 mL
C2 = 2 mg/L
V2 = 100 mL

The operator will now use the variable pipets to add 6.67 mLs of the 30 mg/L add to the volumetric flask and bring the volume to 100 mLs.

We will have all of the unknowns available at WEFTEC. It has not been decided how we will handle the tables or divisions yet.

We are still deciding on how we will handle the unknown. Once we decide it will be fair for all teams.

Yes you can use the pipette if the unknown requires you to use a smaller volume. If that is the case then you will not need to rinse the graduated cylinder. You will need to ensure you use a fresh pipette tip. You will need to rinse the STD beaker with DI water 3X and pour some of the unknown into the beaker and pipette from the beaker into the volumetric flask. I will be updating the procedure to include this in it.

In the procedure, the participants would check the COA standard value on the label of the box of ampules they are provided, and calculate the volume of standard from the ampule that would be needed to prepare a solution with a target concentration of 1 mg/L Cl2 using the concentration on the label. Although I agree that it would be difficult to get good results on that 1 ppm standard if you only know the concentration range of 50-75, but that isn’t the case. You will be able to know the standard concentration with a resolution of 0.1

If and when there are more significant changes I will post and updated procedure.

No if you don’t use a beaker you don’t have to rinse but if someone uses it and it has not been rinsed that will be a penalty.

The unknown that you are calculating for is a rough estimate. The only unknown that would produce a value over the tube limit is the 30. If you get above range on the spec then that is what you would put as your answer and then know that it is the 30. The accuracy comes when you are making your 2 mg/l from the unknown and doing it in triplicate.  Please refer to multiple questions above that explains this as well.

For a 3x rinse you rinse once and dump and do that 3x’s

1. We either need to hear you count or see that you rinsing and the right amount of times.
   
   
2. The judge will make sure they can see the meniscus you don’t have to do anything special with that but if you are blocking then you will be penalized.
   
   
3. Timing is about not leaving things for a long period of time and coming back. For results you can not go on to the next sample before you have written down the result. For rinsing or shaking samples you don’t want to leave it settle back or become contaminated


4. You always label the glassware before you do anything including rinsing so yes it need to be done before you do anything with the glassware.
   
   
5. You are not expected to do both we just want to make sure that you are hitting the 10 ml line.

Please follow the written procedure.

The phosphorus tubes need to have the liquid dumped into liquid waste and the tubes go into the trash.

Piggy backing on the question above, that means we no longer have to calculate the peaks between Chlorine Standard Additions? Just seeking clarity on this as it was given as a penalty in recent event (Not showing Calculations)

Sorry, I mean the peaks in the Chlorine Standard SOLUTION (Part 2 of Chlorine). Many judges (and teams) at the state level are being trained from the video, in which they do that calculation. I'm looking for a definitive 'yes' or 'no' that I can use to challenge a judges decision should we be penalized for not doing these calculations in the future (which are currently not required by the Event Description, but can be issued as a penalty on Judge Sheet #4 - 62)

The bench sheet  shows that you record the 1 mg/L standard 3 X and then you calculate the average of that. You need to show that math on the bench sheet. Then you read and record  the 0.1, 0.2, and 0.3 on the bench sheet.

You need to show your work on all calculations on the bench sheets no where on the penalty sheet does it specify what calculations so any calculations that are used to get results need to be shown.

There will not be a new video this year. The video is used as a guidance please refer to the procedure for how to perform the event.

The paper work will be placed face down after the 2 minute set up and can not be touched until the time starts.

It would not be a penalty but if you read it more than once you need to follow the procedure before you read inverting 3x and wiping it down again before going into the spec or that part can be penalized again.

The powder pillow needs to be added after the sample is added.

You can pour it into a beaker labeled STD. What is in the volumetric flask is a standard.

Yes you can use 150 ml beaker as long as it is labeled STD

Since the beaker had STD rinsing once with a little of the 2mg/L PO4 will be sufficient.

1. The pipettes can end on either table do not place them in the dirty glassware container.
2. Yes you would use the blank that was used to zero for you blank reading.
   
   
   
3. The rounding rule is round 1.56 or 1.58 would round up to 1.60