Pump Planning/Installation advice wanted 1

[RDUK]

Hi all, looking for a bit of advice about replacing parts of an existing system which is so old no-one can remember any details about it!

The requirement is to pump water uphill to a holding tank, approx. 100m above a spring. An existing system is in place, but old, and possibly massively overengineered. My father in law is having the generator in the existing system replace, but a lot of alarm bells are going off (I'm worried he's spending money that doesn't need to be spent, tech has moved on a lot in the twenty five years since installation and it might be a good time to modernise, rather than just replacing).

Requirements:
Water is collected from a spring (and mud settled out) and stored in a tank next to the spring.
This water needs to be pumped up approx. 100m vertical and 500m horizontal traverse to a holding tank
System should be able to pump 1,000L per hour, though that is peak usage, and normal usage would be in the range of 500L per DAY - much lower than peak requirements. (also, it may be possible to reduce that peak requirement to 1/2 or even 1/4 of that rate, currently unknown)

So for those familiar with US measurements... around 5 Gallons per minute going up 100 yards and across 500 yards.
Climate - Mediterranean, altitude is around 500m, in Northern California

All piping and tanks are already in place - the current setup has a pump powered by a 8.5kw diesel generator, which feels massively overkill for the requirements. Current pump unknown (I'd need to get into the tank it's built into, which I can't do for a week or so) but runs ONLY when the generator is on, which is ONLY run when a human is present, which could be as little as six or eight hours a week.

So the current system is engineered to elevate the water required to the higher tank in just a few hours - but it could instead be done potentially 24/7 or during sunny hours with the help of solar, meaning a pump (and power supply) which could be an order of magnitude or more less powerful than the existing system.

Questions I'd like help with as I'm unexperienced in this area:

1] What kind/size of pump would we need to hit that peak flow (5gpm elevated 100 yards, run approx. 500 yards) and would I need to gather any more details to work this out?
2] Would it be more feasible to do this with a small solar/battery installation (unattended) than with a generator (my gut feel says yes)

I'm trying to quickly understand ROUGHLY what we would need and what that might cost before money is spent replacing the curreng generator (which is faulty) which could be a colossal waste of money if a cheaper and better system could be put into place.


Thanks in advance for any advice, your help will be much appreciated!

 

[Artisi]

Is it 100 metres or 100 yards vertical and 500 metres or 500 yards pipe run, what is pipe diameter?

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.)

 

[itsmoked]

This cries out to be solar. The problem with solar normally is storing energy with batteries (expensive) but when water is involved you get to store the energy cheaply simply as water in the tank.

Switching to solar allows the total amount of water to be pumped over the entire day instead of while some one has to stand around. You should be able to pump far more slowly reducing the friction head considerably. That allows for much higher pumping efficiency.

Can an array be accommodated near the settling tank?

Your numbers are whack. If usage is 500L/day then you should need the ability to pump 500L/day or possibly a little more to reach whatever the peak day could ever be NOT 1000L/hr. That sounds like it's only for human standing-around convenience.

With solar you spread pumping over about 5 solar pumping hours/day.
500L/5hrs = 100L/hour. 27gal/hour or 0.5gal/minute!!
That's trivial output!!

In fact..
If geography allows the water to flow downhill from the settling tank there's no reason you couldn't use a simple ram pump to do this job. That removes the need for any fuel or electricity what-so-ever.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Artisi]

RDUK, suggest you look at itsmoked suggestion about hydraulic ram pumps, there is considerable information on the net to review, could well be an good solution for you.

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.)

 

[RDUK]

Thanks kindly for the reply itsmoked - in response to the query about flow rates, the "normal" usage is just to fill a single trough and provide water to a single small home - so the average usage is 500L per day, and tank capacity (at top) at least 10,000L - however there are some times of peak demand, when water is supplied to several households, and in dry times to some other cattle watering troughs.

Realistically, the ability to fill (or at least fill a large chunk of) the top tank within a day is desirable - I figured if we can pump 1000L per hour and there's 8 hours of solar in a day, that would get us a mostly full top tank in under a day. We may be able to compromise on this rate a little, but I'd like to aim to achieve something like that, and only fail if we have to).

I would love to use a ram pump, but the flow from the spring is highly variable, and sometimes we need to pump most of the output up to the top tank - in fact, when the spring is at its' minimum (in drought) is the time we need the most water pumping, so I think the idda of a ram pump is out.

I think 5 hours a day of solar pumping 1000L/hour would satisfy the need here - and yes, I think a solar array can be mounted near the lower tank. I think the feasibiity is there, but I'm not sure what size of pump and wattage of solar array we might need to move water at that rate up the hill. Any back of the envelope calculations that might give me an idea? Erring on the side of "too much power" probably best.

Again, thanks very kindly for your help!

 

[itsmoked]

OK. Yes, ram pumps cost water, which could be limited in your case so back to solar.

You've given info about elevation and lateral direction. Fine. However friction head still has to be figured out. Friction head is the loss caused by the water's velocity thru the pipe and to a lessor extent what type of pipe it is for internal smoothness. The diameter of the pipe controls the velocity against the flow rate.

1) We need the pipe inside diameter unless you know the kind and we can look up what the inside diameter is for that specific type.

2) Since the friction head-loss is applied to every foot of pipe we need a little more detail on the length. What you've described is essentially 100m straight up and 500m straight laterally. I doubt this is what you actually have. Do you have any kind of grade information? 20 degrees average or 45 degrees? What? This will allow an estimation of the total length.

3) The pump is to be fed from the side of the settling tank via a pipe?

4) Do you have pump specs for what exactly is doing the pumping now? This would be very useful. Got a picture of the pump plate and motor plate?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Artisi]

What is the current pump, centrifugal or positive displacement pump?

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.)

 

[RDUK]

Thanks for the replies!

1) The pipe and current pump are unknown right now - I will attempt to gather more information and trace the pipe from the lower tank to the upper tank when I visit on Monday. I'll post updates here regarding pipe diameter and possible the current pump.

2) To be confirmed after Monday, but I have attached an image below which shows the elevation profile of the straight line from the lower to upper tank - I'm fairly sure (but will confirm 100% in a few days) that the pipe follows this route, or a close approximation to it.

3) The actual setup has a small settling tank fed from the spring, and from the settling tank it feeds a much larger storage tank at the same location. I will try to gather more info about the existing pump and how the pump would/could be fed when I visit Monday. At the moment just getting a rough idea of what kind of pump MIGHT be required and how large a solar array - back of the envelope style - would be helpful to decide if this is worth pursuing or not.

4) Not sure what the current pump is, don't have specs - I will see if it is possible to access it easily on Monday

@Artisi: The current pump is (I'm told) a centrifugal pump, and is embedded/installed in the lower tank - if that's accurate I'm not sure how to access it at this time, but will see what I can do.

 

[itsmoked]

Here's what's on my napkin:

This is the USA you're working in so we'll change out of metric.

Static head: 77m x 3.28 = 253ft Vertical
Lateral Distance: 480m x 3.28 = 1575ft = Lateral
Hypoteneuse = 253ft + 1575ft = 1,600ft Pipe Length

1000L/hour / 227gal/min = 4.4gal/min

The flow sets the pressure required for any particular size pipe.

Friction Pressure required using 3/4" PVC plastic => 70ft of friction head | velocity = 2.8ft/s
Friction Pressure required using 1" PVC plastic => 21ft of friction head | velocity = 1.7ft/s
Friction Pressure required using 1-1/2" PVC plastic => 2.5ft of friction head | velocity = 0.7ft/s

Working head with:
3/4" PVC = 253ft + 70ft = 323ft = 140psig
1" PVC = 253ft + 21ft = 274ft = 119psig
1-1/2" PVC = 253ft + 3ft = 256ft = 111psig

Pumping requirements assuming 75% pump efficiency and 90% motor efficiency
3/4" PVC = 0.48HP into the pump. 0.40kW into the motor
1" PVC = 0.41HP into the pump. 0.34kW into the motor
1-1/2" PVC = 0.38HP into the pump. 0.31kW into the motor

A typical solar panel is about 250W but at 9A and 28Vdc. Two panels gets you about 500W. The worst case 3/4" pipe setup would likely need about three panels while the 1" and 1-1/2" PVC pipe lines would probably run with 2 panels.

There is certainly more to do in regards to how to get from the solar source to what the pump needs. There are many ways to achieve it but it all depends on the details we don't have. You also need to have a way to stop the pump at the bottom of the hill when the tank is filled. Choices are; letting it run out on the ground. A wire. A radio transmitter and a receiver at the pump.

If the existing pump is old it may make sense to get a new solar pump system. If it's newish then you need to convert the solar to whatever power the pump needs. There can be some losses involved which might reasonably be expected to up the panel counts by one.

If the pipe is steel or smaller or ??? it would change everything.

Folks, do my numbers look reasonable?
Or as Artisi suggests below these smaller pumps are less efficient so these numbers with a 50% efficient pump would change to:
Pumping requirements assuming 50% pump efficiency and 90% motor efficiency
3/4" PVC = 0.72HP into the pump. 0.59kW into the motor
1" PVC = 0.61HP into the pump. 0.51kW into the motor
1-1/2" PVC = 0.57HP into the pump. 0.47kW into the motor

So around 4 solar panels might be required. At any measure a small system.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Artisi]

Without checking - would say OK, except pump efficiency, for that flow and head and again without checking would be plugging 50% effic. into the calcs.

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.)

 

[itsmoked]

OK, thanks Artisi. I'll maybe crank those numbers when I have some time.

Done. See above.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[LittleInch]

I've done this in metric as it's easier for me and come to much the same answer - i.e for 1000 l/hr you're looking at a pump power of about 450W ( I used efficiency 55% as small units are not as good)

So with a few more motor losses probably about 500W of electrical power.

This is directly scaleable to flow so if you wanted to double it then times by 2.

This post also gives some good advice for something similar and some ready made solutions

https://www.eng-tips.com/viewthread.cfm?qid=459801

There though some things you need to find out / calculate / know about.

Find out:
As best you can the exact head you are climbing up from water level to water level in your top tank when full
The OD and ID of your existing pipe and type of pipe
The length of the pipe
Any restrictions / valves etc
How often you need to fill the tank
How does it work at the moment in terms of control / on/off.
Do you want to automate this?

Calculate:
Pressure drop from flow rate

Think about:
How you want to power this pump
How you want to control it

Whilst a on/off level control would be a good way, it might be easier just to have a timer and set it depending on the level in the tank. If you pump too much then is a bit of an overflow situation a bad thing?

A solar system will only work when enough sunlight is available. The pump simply won't be able to pump water up the hill until you get a certain level of voltage or power.

On the pump side you need to try and match your required head and system resistance ( mixture of static plus flowing head) as well as you can. The temptation is always to "add a bit", but this could mean you seriously over size your pump and end up running off the curve with more flow at a lower efficiency. Maybe not a big problem, but you might want to introduce a control valve of some sort to control flow to match the pump. Also you will need a non return valve.

These guys seem to offer a package solution and there are many others as your duty is quite common in developing countries.

https://www.lorentz.de/

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

 

[RDUK]

THank you everyone for your sound advice - it's been very helpful.

We've found that the existing pump is a 2HP pump, so about 1.5kw draw - we are now investigating a solar plus battery solution to provide power to the existing pump, and have contacted a professional who validates my assumption, and the advice of people on here.

Glad to say it worked, thanks once again for all the ideas and info everyone, it is very much appreciated.

 

[LittleInch]

The battery is really only there to add a bit of starting "oomph" to the pump.

For your 1.5kw pump you would need about 4 normal sized 12 V car batteries to last one hour.

However you need deep draw batteries and the number of amps at 12V is rather high so you end up with some big leads going into your invertor unless you couple them up in series.

Means your 8.5kW generator is rather OTT, but maybe it was needed to start the pump as the motors often take 3-4 times full load as starting current.

Thanks for letting us know it was useful.

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

 

[QualityTime]

Not sure anybody makes a 5 gpm centrifugal pump

 

[itsmoked]

RDUK; How's it going? You might want to run any potential system/quote past us.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[RDUK]

Thanks for checking in, itsmoked - this project has had to go on hold for a while I'm afraid. A lot of the urgency came from a wedding (mine!) that was to be held at the property in 2 months, but this is now going to be a year or two away so our interim fixes can work a little longer. Add that to my father in law being 72 and in California, and we're trying to reduce any time spent around other people (the ranch is super remote, but getting gas and supplies etc. is a risk), shopping etc.

I will update when we get this moving again - an old friend of mine suggested that a lot of the solar tech is getting consumer-friendly to install these days, so as I have nothing to do all year, I may try to educate myself on that and see if we can get a small array & battery hooked up to the existing pump.

Once again thanks for all the help digging into this!

 

[itsmoked]

Congratulations! May you have a long and happy marriage.

Oh yeah the plague and all... Yep, good call staying away.

Well, we'll be around whenever you can get going.

Stay well!

Keith Cress
kcress -

http://www.flaminsystems.com