DESIGN : DEAR MR PLUMBER 27 the cold-water reticulation must be designed with the hot-water reticulation system to ensure equal flow and pressure at all draw-off points .
Back-up / redundancy and operation and maintenance ability with appropriate access ‘ to-and-into ’ the systems is a high priority and very , very , important .
Environmental considerations and requirements must have priority and shall be the basis of the design to save energy and our precious water , and this must be built into the design in compliance with the latest SABS standards .
As I have said , the pipe configuration is a primary , critical , element and here the architect must play an important role to facilitate the best pipe configuration .
The best pipe configuration is the ‘ up-feed ’ system where the hot water rises from the bottom up and to have the return piping from the top down and back to the plant room at the bottom . The ‘ balancing ’ must be at the top of the hot water risers and not at the bottom .
The following is important : Provide air release valves at the top of each riser , with drain piping because these air release valves normally leak water and cause damage .
Note the design parameters , which are as follows :
• Maximum water pressure = 600kPa
• Maximum temperature = 60 ° C
• Minimum temperature at last draw-off point = 55 ° C
• Temperature at draw-off points of facilities for elderly and disadvantaged people , and children , must be limited to body temperature by means of providing mixing valves to limit the temperature for the users .
• The velocity of the water in the piping inside the building and above ground must not be ‘ fast ’ as per Mr B , but at a velocity to prevent water hammer and noise , and it is normally between 1.0 to 1.5m / sec , and for pipes in ground it is normally about 2.0m / sec .
• Pumping ‘ fast ’ has got nothing to do with the balancing .
• The cold-water parameters of velocity and flow and pressure must match the hotwater parameters .
• There are several other parameters which are important , and which are all noted in the relevant standards some of which are compulsory such as SANS10400-XA .
• Another regulation is the specification of the piping insulation to save energy , but I have found that there is a reluctance to apply it and in many houses the piping is just not insulated and in other buildings the insulation is still the old type which does not comply to the compulsory specification .
I do not wish to turn my article into a lecture on how to design a hot water system , but the ‘ engineer ’ responsible for the design should be a registered and competent engineer with experience and able to apply his education in hydraulic and thermo dynamic theory .
There is an old saying : “ Shoemaker , stick to your anvil .” The message is simple , do not present yourself to be who you are not , and do not accept work for which you are not competent .
[ Editor ’ s note : As always , we welcome Vollie ’ s pieces as he does not beat about the bush . Read the last line again and see how it can apply to some of those unqualified people doing plumbing work .]
“ Environmental considerations and requirements must have priority and shall be the basis of the design to save energy and our precious water , and this must be built into the design in compliance with the latest SABS standards .”
May 2021 Volume 27 I Number 3 www . plumbingafrica . co . za