There are many posts on the web, including very interesting ones, which offer great guidance to customers on what to look for when purchasing a mattress. But none of them is specific to the South African market.
Apart from the international brand of mattresses mainly distributed in chain stores, there is a large number of independent manufacturers who supply mattresses of equal quality. Unfortunatly a large portion don't; and produce a product which is not only a waste of your money, but more importantly a serious health concern.
The quality of a mattress is hard to detect. What constitutes the structure of the mattress is actually invisible, hidden behind the material that covers it.
I see many customers lifting the mattress, using its weight and its thickness as an instrument of measure. Others push a fist through to check the resistance it offers. Unfortunately, none of these techniques are an accurate way of determining the quality of a mattress. In fact there is no physical way of finding out.
What should you be looking for then?
First of all it is common practice in SA from all reliable manufacturers to sew a label on the bottom right hand corner of the mattress with information such as the manufacturer's name, the brand, the name, the warranty and the weight restriction of the product. The absence of this label or part of the information it should contain is a warning.
I recently saw a label that only bares the name of the product and a mention of "8 years"... 8 years of what? This is a trick to confuse the customer into beleiving it refers to the warranty. Together with all missing info, the label should clearly read "8 years warranty".
Secondly, manufacturers that offer a service warranty on their products have to provide the buyer with the terms and conditions of such warranty; either in a form of a leaflet that accompanies the bed or made available online on their website. Again, in the absence of written T&Cs... beware.
Finally, do not hesitate to ask as many question as possible to the sales consultant, including comparison between products on the floor. Mattresses are technical products unlike most furniture; a sales person should be able provide you with clear information. If vague or incoherent it is a sign that he/she either does not know the product or is trying to hide something. In both instances, walk away!