Buzzman
Member
gg
The trees were to hide the tank stand, but yes, if your calcs are correct (and in principle they are) then a stand 50m high would be needed.
However.....I have a friend who has a water tower less than 10m high and his shower head pressure is quite adequate - maybe not high 'mains pressure' but adequate - so there is something else going on I reckon.
Anyone got any ideas?
It is the relationship between static head pressure, friction loss and flow rates.
By example, many houses once had hot water header tanks in their roof cavity. The tank's 'head' would vary depending on ceiling height but a static head of 1.5 metres between the header tank and a shower rose could be assumed minimal as an average.
Each metre of static head provides 9.8 kPa or 1.47 PSI. The dynamic head however is equal to the static head less the friction loss of the water flowing through the pipe. The friction loss will vary depending on the pipe diameter, the type of pipe and the fittings and bends in the pipe. Other factors also influence friction loss including the fluid's viscosity and temperature.
When a pipe's length and the number of bends etc is known ( each 90 degree bend will add about .7 of a metre to the pipe length friction loss calculation), the maximum flow rate to the shower rose can be calculated from friction loss tables. The pipe length calculated can often be double the actual pipe length.
If the flow rate was calculated as being a maximum of lets say 12 lpm but the householder wanted 15 lpm, it may still be enough assuming that cold water would also be used. If not, the flow rate could be increased by lowering the friction loss by using larger diameter pipe or reducing the length of pipe. Delivering too much flow (large pipes) would result in an unusable excess.
ghostgum
Member
You don't need 5-7 bar. I grew up with a briquette hot water heater (neighbours didn't like it, especially on washing days), and the header tank was in the roof. So we only had 1-2 metres of head (0.1-0.2bar) to the shower rose. The shower was adjacent to the hot water heater, so the pipes were really short. It worked fine, until someone flushed the toilet. The hot water had low head, but the cold water was mains pressure, and any other use of hot water or cold water in that house resulted in wild fluctuations in the shower temperature. Turning on the laundry hot water tap would result in a cold shower. Never ever have a shower while the washing machine is running.
If the hot and cold are both at mains pressure, and the pressure reduction occurs in the low flow shower head, then you get far less variation in temperature and flow when other household taps are used.
Yes, in some applications lower head should be fine. Our hot water in London was ultra-low head at something less than 1m but it was really too low for effective showering. No wonder the poms all took baths...
Speaking of water pressure - our first flush is a vertical 90mm storm water pipe and when you open the valve at the base the pressure and hence flow rate is quite considerable! Max static head would be about 2.5m and at that pressure it really spurts out through any small crack/gap.
Water for thought!
http://www.youtube.com/v/LzXrmioDk9U&hl=en_US&fs=1&
http://www.youtube.com/watch?v=ADVB3DqEYK0&annotation_id=annotation_613172&feature=iv
Power usage is interesting, with a lot of misconceptions.
A greywater system, running relatively low pressure (say 8m head) is best srved with a 330w - 660w pump (less than a typical pressure pump on a tank, although there is no need to use a pressure pump if using efficient dripperlines, which are at least 50% more water efficient than hosing / sprinklers in any case).
Additional startup consumption is so small to be immeasurable over a 2 second period.
What is interesting is that a 660w pump actually consumes about 400w during use.
A greywater system, with 4 people in the house, generally runs for no more than 0.5 hours per day (if proper greywater irrigation lines are used - irrigation rate is faster than the inflow rate).
Basically the results are 2 kwh per kl of water, or about 0.26 cents per day $$ cost.
I found it facsinating that Nevada water was proud of the fact that their offsite treatment plants (providing class A back to the household) cost approx 10 kwh per kl, and they had been claiming it was the most power efficient method.
Their jaws dropped when I gave my presentation at the Symposium.
If you want more information go have a look at some of our USA info http://www.besthomewatersavers.com/pages/Graywater-Guide.html
Of course factoring in the infrastructure cost of offsite treatment just makes the case stronger for localised water re-use.
Previous postings prior to the above advert for a grey water system included references to residential water pump start up energy demands.
The Energy Consumption Discussion Paper prepared in 2008 for the Queensland Water Commission quotes Gardner et al. (2006) as showing that small electric pumps suitable for rainwater tanks have a start up energy demand approximately 4 times that required during operation and is a major component of the overall energy consumption.
The Discussion Paper further states that during trials, regular cycling showed an average energy efficiency of 2.9 MWH/ML which equated to approximately 6% of the total energy consumption of the average household. Reducing cycling was able to cut energy demand to 1 MWH/ML or less.
As the above poster claimed in the thread 'Forum Rules' that he is "a leader in greywater irrigation technologies", perhaps he knows something that acknowledged experts do not! Regardless, I question his posted observations:
"Power usage is interesting, with a lot of misconceptions".
"Additional startup consumption is so small to be immeasurable over a 2 second period".
I also noticed on the above poster's website that a product advertised as suitable for the storage of greywater was equipped with a pump and a hose. The company U.S. website also has a page advertising a greywater system which shows a hose being used. The U.S website was also linked on other ATA forum threads by the above poster and as such was advertised to ATA members and forum readers.
In Australia, it is strongly advised that greywater should NOT be distributed by a hose or sprinkler for health reasons. Hosing/sprinklers are also mentioned in the above post but there is no recommendation in the post that such use should not be practiced.
