Pressurised vs Towers Advantages/Disadvantages
Pressurised vs Towers Advantages/Disadvantages
(OP)
What are the advantages and disadvantages when comparing a pressurised system versus a elevated tower system for water distribution?
I have considered that
1)sizing pumps for fire duty is one disadvantage for the former.
2)use off peak energy versus off peak energy is a disadvantage of the former.
3) need to size pumps for flushing?
Do members have any other ideas?
I have considered that
1)sizing pumps for fire duty is one disadvantage for the former.
2)use off peak energy versus off peak energy is a disadvantage of the former.
3) need to size pumps for flushing?
Do members have any other ideas?





RE: Pressurised vs Towers Advantages/Disadvantages
2. Capital costs will be higher for a water tower system.
3. It is easier to control system pressure with an elevated tower.
4.
RE: Pressurised vs Towers Advantages/Disadvantages
RE: Pressurised vs Towers Advantages/Disadvantages
RE: Pressurised vs Towers Advantages/Disadvantages
Personally I think the consultant is adopting this approach as a pressurized system requires more engineering at the expense of reliability.
There is a very good report from the Asian Development Bank that criticizes conventional wisdom in bringing water to the urban poor in Southern Asia. The consultant seems more imterested in there own livelihood than the poor.
RE: Pressurised vs Towers Advantages/Disadvantages
Sounds to me like your well known consultant should be investigated by the client countries to whom this kettle of fish is being sold.
You may have to demonstrate the obvious to thos countries to unmask these guys.
good luck
RE: Pressurised vs Towers Advantages/Disadvantages
Gravity always works.
No control system (no mater how well tuned) can keep pressure as smooth and flow as responsive as gravity in a large at service level tank.
If reduced pressure is allowed at low demands nothing says you have to have just one tank, using two tanks at different elevations in the same control scheme (as the pumps would have been engaged at) will save even more power.
Hydrae
RE: Pressurised vs Towers Advantages/Disadvantages
Given the pumps for both types of systems have the same efficiency, the energy (KwH) needed "(Q*H/%eff)*.746*Time" for one days useage doesn't matter if the pump rate is 1000 gpm or 500 gpm. It will be the same.
A proper gravity system will have a greater storage available for extended use; therefore, a smaller pump sized for longer peaks can be used to fill the storage over a longer time.
The pressure system has less storage and requires a larger pump that can meet the shorter peak useages which will be higher (ie. An hourly peak use will be higher than a daily peak use).
The increased start/stop of the pumps will reduce their and their controls (starters) life expectancy thereby increasing the maintenance and replacement costs.
If gravity systems are bad and inefficient, why do all large and almost all smaller municipalities use them?
RE: Pressurised vs Towers Advantages/Disadvantages
I'm not a water system designer, but I would assume that the extent to which people water yards (everyone, all summer around here) and the extent to which water is expected to be used for fire protection would influence the decision.
RE: Pressurised vs Towers Advantages/Disadvantages
With a tower you have a set of pumps that pump into the tower - fixed head - if one pump cannot maintain the tank full then the next pump starts etc. At peak demand storage in the tower contributes to demand and total pump capacity may be less than peak demand. Pump costs are less with a tower!
It would appear that your consultant is proposing a much more sophisticated operating system with the pumps adjusting to the system curve - lower pressure in the system at low demand - variable speed pumps??. In this case there may be significant savings in power and also reduced leakage losses but I would guess that the solution is too sophisticated and not appropriate but It is not possible to give a judgement without some knowledge of the overall system.