Supplying a 200ft structure with water. Single pump or boosters or ?

[fluctuations99]

Theoretically I am needing to get water to the top of a ~200ft structure while also supplying two units along the way. The top of the structure will just need to be able to supply water when needed for general use and occasionally hooking up a pressure washer (40psi, 3gpm typical?). The water at the top will only need to be used every few weeks. However, I also need to supply a 10gpm unit 70ft up the structure and two more 10gpm units 120ft up the structure. These units will need water flow at all times.

If I have single pump that can meet the whole systems demands, will it deadhead the pump since the top of the structure will not have flow? Should I use a VFD for when we need water at the top and just meet the demands of the units for the majority of the time? I also am not sure if break tanks and boosters should be used in this scenario. Just wanting to know how some of you would approach this problem.

Thanks

 

[LittleInch]

First off find out what is feasible and main data.

What is incoming water pressure?
Can you mount intermediate tanks on the structure?
What are pressure requirements / limitations on the intermediate water users?

If these users at intermediate levels are continuous, I think you're better off with three pump units specifically aiming to get highest efficiency possible. Trying to get this level of difference efficiently is too difficult. When you work out operating costs it makes sense to do it this way for continuous applications.

if the pressures and structure allow then I would go for a buffer tank somewhere above 120ft to feed the other users by gravity and then use a small booster pump from the tank to service the occasional user on the top. You can size the pump for the just above the continuous flow and control on level in the tank.

You want to avoid putting energy (pressure) or lifting it high and then loosing that energy by throttling it on a continuous basis

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Artisi]

Alternately, pump to a storage tank at 200ft and reticulate water to the 2 lower levels. This way you can size a pump running at or very near to its BEP.

Using a storage tank you can size it and set the on / off pump / tank levels to suit demand with the pump only required to fill the o/head tank, no need for VFD of fancy control systems .

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[LittleInch]

but at 200 ft it wouldn't have any pressure to feed the item at 200ft and maybe too much pressure for the units at 70ft ??

Too many unknowns at present.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Artisi]

Supply a small dedicated pump at 200ft level for your occasional needs.
Pressure reducing valve/s will take care of the lower levels.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[LittleInch]

I agree, but my point was that the pressure reducing valves simply leak away the energy you've used getting the water to the top of the building in the first place. For domestic / occasional use, fine, no problem, but the OP talks about "These units will need water flow at all times." which I interpreted as being continuous flow. There's no point optimising the BEP of the pump to get water to 200ft high if you promptly lose a lot of that energy by having pressure regulating valves.

As said - not enough detail to know which or what is best for this location - 3 separate pumps and no tanks, 1 pump and 3 tanks or anything in between....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Artisi]

always a compromise, especially without any real data to go on.
Best bet is to contract out the problem to a company specialising in high-rise water reticulation systems -- probably been done 100's of times.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[Artisi]

LittleInch and OP: would be a good exercise to calculate all the costs associated with 1 pump to 200ft and then reticulation against maybe 2 or even 3 smaller pumps complete with control gear, cabling, on going maintenance etc. especially if it's a critical service that might need backup pumps. For me, I would prefer a neat 1 + (1 stand by unit) running constantly at it's BEP in place of maybe 4 or 6 smaller (usually less efficient hydraulically) units. Ok - with a 1 pump installation there is need for a small unit at the upper level for intermediate use - but this could be a small unit from the local hardware shop.

Food for thought for the OP.


It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)