Airlift pump calculation

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manu
Posts: 16
Joined: 15 Jul 2019, 14:40

Airlift pump calculation

Post by manu » 14 Sep 2019, 09:13

I am looking for a pump that will deliver 8000Litter per hour of water to a height of 30cm.
It is important to limit flow rate to 8000 as it will exhaust the wetland filters ability I am using otherwise.
Pool depth of 182 cm and could be increased if needed.
Airflow is fixed at 1.2CFM(2.1 METERCUBE PER HOUR).
What diameter pipe should I use to do this.

Ted1234
Posts: 5
Joined: 09 Sep 2019, 03:49

Re: Airlift pump calculation

Post by Ted1234 » 14 Sep 2019, 15:25

Hey Manu. Airlifts don’t seem to be good at moving water up vertically, even 30 cm, so you might want to look at a traditional pump if that is the need.

That said maybe you could set up your filter such that it doesn’t need to raise the water 30cm. Would that be possible?

Also what type of wetland filter are you using? I would be interested in knowing more about that.

manu
Posts: 16
Joined: 15 Jul 2019, 14:40

Re: Airlift pump calculation

Post by manu » 15 Sep 2019, 14:28

Ted,
Yes,you are correct the main use of airlift is volume flow and not to create a pressure head or lift water. Being said that they can create pressure head of 1 feet without much issue but the compromise being reduction in flow rate.
Initially I was planning for a massive flow rate too with traditional natural swimming pool ( where water just circulate through planted area). This should be enough for most places away from tropics. The planted area needed for such a system is anywhere between 50-65% of swim area.
In tropics like where I am or where land is limited a wetland filter is able to save some space(Filter area needed is 40%). A wetland combines the benefit of circulating of water through planted area and also uses percolation for biological filtering. The maximum water flow rate through the filter bed should be limited to 300Litter/m2/hr for this system to be effective.
For my design this translates to 10,000-11,000Litter /hr of water.As you can see all the designs described here starts at 15,000litter/hr.Moreover I already purchased a pump that delivers 1.2CFM air(SLL30 OR SLL40),so that is fixed.
I guess at this point most effective way to reduce flow is by making the airlift to lift water,which in turn could be used for a small waterfall that may increase oxygenation(may be)or visual appeal. hope this explains why I am looking for options to reduce flow.
I will update detail of wetland filter in another post.Stay tuned.

Ted1234
Posts: 5
Joined: 09 Sep 2019, 03:49

Re: Airlift pump calculation

Post by Ted1234 » 15 Sep 2019, 20:34

Hey Manu,

This sounds like an interesting project. Is the goal for swimming? What area of the world do you plan to build it? Do you have any sketches of what you are planning? For what it’s worth I found uploading pictures to be a pain, so if it saves you some time I found a good option was https://imgbb.com/ and then select BBCode Full Linked.

Also I’m wondering if there are any eventual maintenance issues with doing percolating style filtration, where the medium eventually gets clogged. Have you found any good information on that?

Ted

manu
Posts: 16
Joined: 15 Jul 2019, 14:40

Re: Airlift pump calculation

Post by manu » 16 Sep 2019, 01:02

Hi Ted,
It is a swimming pool and can handle intermittent use by less than 5 adults.it may be able handle more regular use when the filter get mature over few months to an year.
I am still in designing phase.
So there are two possible ways of using a percolating filter from bottom up and top down.
Bottom up will need a pump that can generate pressure so is not an option to use airlift.
Top down is when you put water to be filtered on top and collect at bottom using gravity, where airlift could be potentially used.
I am working with an architect as a lot of materials needed are hard to source in Kerala, India where the pool is going to be used.
Where are you located ?
In terms of maintenance this type of filtering is the least expensive method and life of filter is likely 15 years or so.
If you use upside down flow the top part will have bog formation eventually( similar to natural process) and need top layer removed with replanting of filter plants etc. how often depends on environment, pool’s use etc, but you can assume every few years.
We can avoid extensive pre filtering with topdown as the sand bed itself will be doing it.
We can sample an area every 4-5 years and see if the deeper layers need cleaning in that case take all the filter media out, wash the coarse gravel and reuse with new layer of fine gravel.
Advantage is chemical free water and environmental friendly pool.

manu
Posts: 16
Joined: 15 Jul 2019, 14:40

Re: Airlift pump calculation

Post by manu » 18 Sep 2019, 19:02

Have some good news. After some search and reading about theory I went back to this excel sheet
http://api.ning.com/files/5sXTPNNd5jk1j ... lation.xls
I validated finding on this document in page 6 using the above calculator and seems to be in close match.Lift is 0.8 feet and submergence 6 feet.

Over all this sheet will give you the flexibility to play with submergence depth and tube diameter as mostly airflow rate(cfm) and pressure rating are fixed for a given pump in real life.
Also make sure you are not exceeding pumps pressure limit max by ( best to keep it at 80% rating to account for friction and water height losses) any means.

I feel the administrators should somehow make this excel sheet saved somewhere so everyone can download and try it and validate findings.

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Pssymon
Posts: 171
Joined: 11 Dec 2015, 00:12
Location: The Netherlands

Re: Airlift pump calculation

Post by Pssymon » 21 Sep 2019, 21:20

Hey Manu,

Thanks for sharing that file. I've seen it (or a similar one before).
It's interesting, but I can't vouch for it completely. I agree that it would be a good idea to share it on the site, you just did, but I understand what you mean, I could make a 'sticky' topic for it in the future. As long as we do not change the file and credit the author this should be okay.
I do however want to wait until I can check my findings with this sheet. For now I am not yet able to do this, and I really want to make sure I do not spread information that I cannot support with a 100% certainty. Although this sheet looks very credible, I would like to make sure with some tests first.

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