# How to calculate PIR

**Summary: **
A Guide for those confused by PIR and a quick way to calculate it

## What is needed for calculating PIR?

This is much easier to calculate using metric measurements because in metric 1 L equals 1 kg. We recommend calculating all of your Panel Impact Ratios (PIR) in metric.

- Pressure washer and foam cannon
- Empty bucket
- Measuring beaker
- Scale

## Steps for calculating PIR

- Start by filling your pressure washer bottle with exactly 1L of water and set your gun to your preferred setting.
- Weigh the empty weight of your dry bucket. We'll call that value "mdry".
- Run your pressure washer with the foam lance on it into the bucket until the bottle is used up completely.
- Weigh your bucket - we'll call this value "mfull". If you don't have a scale, you can also use the beaker and measure how much water you have taken out or use a bucket with an internal scale.
- Calculate the weight of the bucket by subtracting the weight of the empty bucket (mdry) from the weight of the full bucket (mfull-mdry=mwater). Now as PIR is mostly given in percent, you want to divide that result by 100 to get 1% (mwater/100=1%PIR)
- If a product calls for x% of PIR you multiply x by your one percent number, then fill your bottle with that amount and fill it up to full (1L) get to the exact value. Be sure to mark the settings used on your pressure washer to be consistent.

## Example PIR Calculation

Lets do an example calculation with totally made up numbers. These aren’t meant to match yours, so don’t worry if they deviate.

Your empty bucket weighs mdry = 1500 g and the full bucket comes in at mfull = 14600 g.

Now first we want the weight of the water so we subtract (mfull-mdry = mwater) 14600 g-1500 g = 13100 g

Great! now we have our amount of water, which is 13100 g or 13.1 kg or 13.1 L of water. Now we want to know what 1% is so we divide by 100 (mwater/100 = 1% PIR) 13100mL/100= 131 mL.

Let’s say we want to make a 4% solution, so you take that value by 4: 131*4 = 524 mL which means that you put 524 mL of cleaner in your foam cannon, then you add up to the full Liter.

Either you fill up to the full Liter mark on your bottle or you add 1000-524 = 476 mL of Water. **Please remember that these numbers are just examples to show the math.**

## PIR Questions

*Could you theoretically make less then a Liter of prediluted Product in your Foam gun ?*

Yes you absolutely can, but you need to keep the ratio of water to concentrate.

*But what if you have a product that states a PIR but you want to use it from a foam or pump sprayer?*

In that case what you see is what you get, so fill in the correctly to percentage diluted chemical in the Sprayer