Q&A
The quality of the sand in sand slits determines how well they do, or do not, drain.
Water does not “flow” rapidly in the slits - "seeps" through and along them.
it
Only if the selected sand is suitably permeable, will water move at a rate required for good drainage.
Less permeable sands provide dis- proportionately poorer results and usually are not cost effective.
It is essential to ensure the sand used is analysed and tested so that it really does meet requirements.
What SAN
Question 1 There are many different types of sands . Which are most suitable for Sand Slits? Answer 1
A sand which is tested and shown to:
1. Contain almost no particles larger than 1mm in size
2. Contain no more than 0.2% fines (less than 0.063mm).
3. Have a high percentage of its particles in a single mid size category.
4. Have a Hydraulic Conductivity in excess of 1,000mm/hour. (A figure of 2,000mm/hour would be exceptionally good.)
Question 2 Where can such sands be purchased? Answer 2
It is essential to insist that the sand conforms to the four points listed at Answer 1 above.
Local sources of these sands may not exist in some areas but to find a supplier is essential, therefore time must be spent in establishing the nearest contacts.
Very few local quarries or builders merchants can supply suitable sand.
There are specialist companies who do deliver in all areas, although transport costs are high where long distances are involved.
Yellow Pages, sportsturf magazines and similar journals usually contain specialist suppliers advertisements giving addresses in different regions.
Question 3
What will it cost per tonne? Answer 3
A suitable sand can be double the price of a not so good one, but its greater effectiveness makes the dearer sand better value.
For example - A good sand with a hydraulic conductivity of, say, 1,500 mm/hr costing £24 per tonne is five times more effective than a concreting sand costing £12 per tonne but which has a hydraulic conductivity of only 300mm/hr.
Question 4 How much sand is required?
Answer 4
Straight forward arithmetic can translate the total linear run of the slits into the m3
quantity of sand required:
Width of slits x Depth of slits x linear metres = m3
required.
Depending on moisture content, 1m3 weighs approximately 1.8 tonnes.
Example 1
10,000 linear metres of mini sand slits, 18mm wide x 150mm deep.
0.018 x 0.150 x 10,000 = 27m3 x 1.8 =
48.6 but say 50 tonnes required. Example 2
3,000 linear metres of major sand slits 50mm wide x 300mm deep.
0.05 x 0.300 x 3,000 = 45m3 but say 84 tonnes required.
x 1.8 = 81
It is better to order slightly more than the theoretical quantity; there is always a little “spillage”.
Question 5
Bagged kiln-dried sand flows easily. Bulk deliveries of other sands are often moist and tend to block in the hoppers of the
A suitable sand can be double
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