# Volume Calculator for EGFM

The size and depth of EGFM required is exactly the same as if you were using conventional filter sand. EGFM is only 85% of the density of filter sand so if you know what the weight was in the filter originally just multiply this by 0.85 to calculate the weight of EGFM you require.

If you don't know the weight then you can use this volume calculator to help you work out how much EGFM you require. To do this you will need to work out :

1. The area of your filter
2. The grade and depth of media you need in your filter
3. The total weight of EGFM required

### 1. Calculating the area of your filter

To begin with you need to measure the diameter of your filter which will enable our calculator to work out the area of your filter.

 Filter Diameter (m) Filter Area (m²)

Now you know the area of your filter you need to ascertain how much filter media is required for your filter. To do this you will need to establish the bed depths you need for the various grades of EGFM.

### 2. What depth and grade of media does my filter require?

A bed depth of 1m is normal for medium-rate filters whether it is a single-grade filter or a multi-grade filter. The grade of media that makes up the bed depth depends on the design of the collection system in the bottom of the filter.

If the filter has nozzles at the bottom of the filter it will require two types of media grade 3 (6mm) at the bottom and grade 1 (16/30) above it.

For example a standard medium-rate single-grade filter with a bed depth of 1m would normally be divided into 700mm of EGFM grade 1 and 300mm of EGFM grade 3.

If the filter has laterals (pipes) with holes in the sides (usually 6 mm) a graded bed is required with up to 6 layers of media. 40 mm pebbles at the bottom through to grade 1 EGFM at the top.

For example a standard medium-rate multi-grade filter with a bed depth of 1m is usually split into 490mm of EGFM grade 1, 130mm of EGFM grade 2, 65mm of EGFM grade 3, 65mm of 10mm pebbles, 85mm of 20mm pebbles and 165mm of 40mm pebbles.

Once you have established what type of filter you have you need to work out the different bed depths you require of the various grades of EGFM and pebbles. (Please note if you have a single-grade filter you will only need EGFM Grade 1 and EGFM Grade 3). These depths can then be entered into the calculator in step 3 to work out the total amount of media required to fill your filter.

### 3 . Calculating the total amount of EGFM required

The calculator below will calculate the total amount of EGFM and pebbles you need based on the bed depths you opted for in step 2.

To use the calculator:

• Enter the bed depths for all the different grades of EGFM and pebbles your filter requires.
• Click 'calculate' and the calculator will use the area of your filter (from step 1) and the density of the media to work out the total weight of each grade of media needed to fill your filter.
• As all EGFM and pebbles are sold in 25kg bags the calculator will also calculate the number of individual bags required.

 Media Type Density of Media Bed Depth Required (mm) Weight Number of Bags Required Grade 1 EGFM (16/30) 1.35 Grade 2 EGFM (8/16) 1.35 Grade 3 EGFM (6mm) 1.35 10mm Pebbles 1.6 20mm Pebbles 1.6 40mm Pebbles 1.6

Once you have calculated the number of bags required for your filter you can then contact us for a quote!