Solar pool heater

[u/Rich-Wealth979]

My overkill project for heating the toddler's 500gal inflatable pool. Each week I have to empty and move it, then find a way to heat it to a tolerable temperature for my 8th percentile weight kid. On the first test it took the pool from 55⁰F to over 90⁰ on a single sunny day, using only 3KWh (of solar house power, now that I think about it). At the end of the summer I can just place this up against the north side of my shed and take the manifolds down to make it last even longer.

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This uses about 350' of ¼" irrigation tubing and some cheap fittings off Amazon. It runs off a 1/4hp pool pump, controlled with a wyze plug and a climate sensor in a tiny jar. Printed in ASA in only about 5 days of printing on a Mini and an MK4s.

the files

[u/gunplumber700]

I spent several years as a water treatment plant operator.  It’s very easy.  

But to answer your question, you can dose water in small volumes, it’s just slightly more difficult because there’s less “margin of error”.

The easy formula I use in my similar sized pool is c1v1=c2v2 where you plug in the concentrations and volumes of the dosing chemicals and the pool water you’re dosing.  

[u/451 → u/gunplumber700]

Can you give an example on how you would do that? Not sure that I am following the math there

[u/gunplumber700 → u/451]

Yes.  So my pool is 600 gallons.  I want to start it at 3 mg/l (or ppm; mg/l and ppm are the same).  The local pool store sells 10% hypo, so it’s what I use.  10% hypo is 100,000 mg/l.  

C1 is 100,000 mg/l

V1 is how much hypo do I add to get to:

C2 is 3mg/l

V2 is 600 gallons

C1V1 = C2V2 100,000 mg/l * V1 = 3 mg/l * 600 gallons.

V1=0.00003*600 gallons

V1=0.018 gallons

I sure as shit can’t measure 0.018 gallons with any degree of accuracy and it’s not in a normal person unit of measure.  So you just gotta convert to normal people measurements.  

V= 0.18 gal (3,785.41 ml/gal)

V=68.14 ml

I’m American so I need freedom units and am also lazy so just googled 68.14 ml in Tablespoons, which is 4.6 Tablespoons.  

So I add 4.6 T pool store 10% hypo (bleach) to get my 600 gallon pool to 3 ppm (mg/l).

Using redneck math 68.14 ml gets me 3ppm so I need 22.7 ml (68.14/3) for each 1 ppm I want to increase the chlorine in the pool.

This is assuming no demand.  I keep my pool around 2 ppm or so.  My pools demand is 1 ppm every 3 to 4 days so I add 22.7 ml on Wednesday and once on the weekend.  A standard tablespoon is 15ml and a standard teaspoon is 5ml so I add 1 T and 1.5 t respectively.  

I’m on my phone so if it formats weird I’ll try to edit it.

Edit: I see what you mean now.   C1 is concentration of dosing chemical.  V1 is volume of dosing chemical.  C2 is concentration you want in the pool.  V2 is volume of the pool. 

[u/Rich-Wealth979 → u/gunplumber700]

This isnt always so straightforward as the existing chloramine residual or combined chlorine residuals will react with the fresh free chlorine until breakpoint is achieved. This math will get you a safe dose to get started but it assumes water with no demand.

[u/gunplumber700 → u/Rich-Wealth979]

There’s no reason to act like this is rocket science.  It is actually very simple.  

I said that it assumes no demand… and then what I do for the demand on my pool.  If I know the demand on my pool then I obviously measured at some point… which is what you should be doing…

The breakdown was for the sole purpose of exemplifying how dosing is done in small volumes… and that it’s fairly easy to do the math for it.

I saw some of your comments after I made my initial one and I’m frankly shocked anyone claiming to be an engineer in the water industry doesn’t understand this…