A manhole is constructed with the purpose to collect waste materials and waste waters from the household in areas where there is no public sewer system. The construction of the manhole alone depends how well it will function, i.e. how often one might experience a Blocked manhole Harrow. Of course, a Blocked manhole Harrow can also be caused by the waste materials released into it. There are different waste materials, so members of the household should be aware of the fact that not all waste materials should be released into a manhole. Let’s provide some useful info about waste materials and waste waters that will provide helpful hints in deciding what should be released into a manhole. Waste waters are actually a mixture of different impurities. The quality of waste waters depends on their origin (i.e., where they were created – communal, household, industrial, processed, etc.). The main indicators of waste water quality are: 1) solid residues 2) spread (suspended) and dissolved substances 3) microorganisms 4) nutritive salts 5) persistent substances 6) poisonous substances 7) radioactive substances 8) dissolved gases 9) increased water temperature 10) other contaminations Solid residues are paper, rags, fruit remains and other larger organic and synthetic residues. Oxygen is used to dissolve organic residues, which causes a lower level of oxygen in the water. Spread and dissolved substances in waste waters are of organic and non-organic (mineral) origin. Spread substances are larger particles than dissolved substances that are in waste waters present in the form of ions and molecules. The transition between spread and dissolved substances are colloids. Spread and dissolved substances change the water color, while spread substances and colloids cause fuzziness. Increased water fuzziness prevents light penetration, which slows the process of photosynthesis. This is why there is less oxygen deeper in the water, which increases the zone of anaerobic dissolution of organic matters, which subsequently leads to the creation of unpleasant-smelling gases. “