Trying to build small homemade pool -- need guidance please

[bk406]

BTW, my thermal ciphering definitely is suspect because it also predicts that it would take 2 weeks for the water to cool from 90 to 80 in 30 degree ambient average.

At 30 degree air temps, even with a solar cover, you will lose 10 degrees in one night, two at most.

To raise 52,000 pounds of water 10 degrees, it will take 520,000 BTU. Thats a lot of BTU for what your describing. I dont think you will generate anywhere near that. For your small pool, you could get a 400,000 BTU gas heater and heat that pool very easily. For propane, that 10 degree rise would cost around $13. For natural gas, maybe half that.

 

[BillRussell51]

My current daydream is to pipe warm air from a wood-fired hot air furnace.

Current: What do you folks think of this skimmer arrangement? (I had to reduce the clarity of the cannon image for the website.

 

[bk406]

It wont be near enough BTU. A little warm air wont heat it much at all. As I posted before, you will need hundreds of thousands of BTU to heat a pool.

 

[BillRussell51]

Bk, Thank you for helping me. We are in a rural area and do not have natural gas available. Whatever fuel will have to be brought in on a truck. I respect and understand your skepticism. For now, I'm trying to insulate the structure as well as possible. I'm also going to work hard to make sure that 2 to 3 feet of dirt under the apron stays bone dry, for thermal purposes. Beyond that, I'll have to experiment to find the least expensive way to inject BTUs. Since I'll be pumping the water around in volume anyhow, some sort of boiler may be required in the filtration circuit. It'll have to be oil or propane fired, unless I can make the wood work. It probably sounds naive, but we have all this dead wood lying around. I'm playing with the idea of a (Fisher 'Mamma Bear') woodstove inside of big welded steel box, both of which I happen to have on hand, combined with a furnace blower. My experience indicates that that stove will produce 1-3 hundred thousand BTUs when its rolling along. The issues will be: a) how much of that can I capture and transfer to the water b) do I really want to fire it at midnight. I agree with you that it is a very large heat load, and that my thoughts are quite ambitious. With oil at 3 buck a gallon, it is a tough nut.


Right now, I'm focusing on the insulation of the structure and plumbling circuit. If I can ever get it warm, I'm hoping the heat won't bleed off so quickly. I'm thinking to using 4x8 sheets of 2 inch styrofoam on the surface, under a blanket. I suppose I can keep stacking those panels until I get the loss to where I can handle it.

It is all a great big experiment. I have no idea how effectively I can transfer the heat from the firebox to the water. If I can't transfer half of it, it is going to be an uphill battle.

Thanks again,
Bill

 

[duraleigh]

Proceed with caution. Heating even a small pool like that takes a stunning amount of BTU's.

Sorry to dampen your enthusiasm, but you will be disappointed trying to heat the pool in the manner you are considering. I have tried it.

The amount of seasoned hardwood you will have to burn will astonish you.

I burn wood to heat my entire house, Bill, and don't even consider using dead wood....it is a terrible source of BTU's

 

[BillRussell51]

I'll have to admit to you both: a 3000 btu electric heater with a plastic tarp cover is barely keeping the masonry from freezing... don't have a thermometer in there, but I'm guessing 40F. ..

Thank you both for trying to help me. I really dread having to buy propane..

I have not been able to find good thermal numbers for dry earth. So the key unknowns in my planning are a) the thermal conductivity of bone-dry clay, and b)how much leaking the pool will do, and c) whether or not I goofed up by not using the styrofoam beneath the slab. (Since it was 'monolithic slab' style, I couldn't get comfortable resting the whole structure on the styrofoam. So I have NO insulation beneath the gravel bed. I have no experience with the plaster materials or sealing this type of structure from seeping. If the pool itself leaks, it will ruin the thermal characteristics of the surrounding earth, obviously, aside from being a water-level headache. I suppose I can use a plastic liner if I can't get it sealed properly. Insulating the top and sides seems pretty straightforward, albeit expensive.

No one is objecting to the corner mount on the skimmer...

 

[Bama Rambler]

I don't object to the corner skimmer at all but I would make sure it's on the side opposite the prevailing winds in your area.

 

[BillRussell51]

Re: Trying to build small homemade pool -- need guidance ple

Well, it took me a while; and it is not nearly done. The bum knee is long ago on the mend. Whatever.
(His mouth is hanging open because he's carrying a tennis ball back up in there. The ball is the thing, you know.) A plasterer I'm not.

 

[Noggin]

Re: Trying to build small homemade pool -- need guidance ple

That is freaking awesome! Good time to be a dog

 

[Casey]

Re: Trying to build small homemade pool -- need guidance ple

My lab mix loves to swim! She would definately give you 2 thumbs up if she had thumbs!

 

[BillRussell51]

Some data of interest to pool designers

Welp, I can now give up some data that might be of interest. I'm finding that, in fact, my planning is working out better than expected regarding heating. I'm finding that I can actually keep this small pool 6000 gallons quite warm with deadfall firewood with a little effort. For the designers in the crowd, my assessment is that the 2 inch styrofoam boards outside the concrete (cinder block) walls is probably quite important.

I'm finding that by running the fire perhaps every other day through the daylight hours will increase/maintain the water in the 70s. I've added an automotive radiator in the heating chamber, and plumbed the filtration water through there. And the heat is still not totally free. To heat, I have to run about a KW of electricity to turn the two fans and the pump. But, for me, its worked out pretty well. I'm pleased. I'm probably not all that objective, and it is a little bit of a case of special circumstances, but there's data here that might be extrapolated by competent engineering. The bottom line, a very small pool, carefully built, can be heated throughout the winter with free (trash quality) wood and for me, it seems a pretty good set of trade-offs.

BTW, I can also confirm that building a pool in the woods is a really dumb idea, and that most family pets are (to my surprise) not at all familiar with swimming.

PS The heatloss with all of the heating stuff cold for 48 hours is 1 degree F per 24 hours. Thats with 2 inch 4x8 styrofoam casually place on surface, with 1 'blue tarp laid over those, under an unheated homemade greenhouse hoophouse (very leaky). My arithmetic had predicted 1.5 degrees per day. Its been mild here, dipping into the high 30s at night and drifting up into the 50s during the day.