Pond Boss Forums AERATION Systems questions Air Temp versus Ground Temp

Many posts I have seen on aeration include caveats like "don't aerate in the Summer when the air temperature is too high" or "don't aerate in the Winter when the air temp is too low." However, unless you run your air line directly from your compressor or windmill into the water, wouldn't the ground temperature modify the temperature of the air being delivered into the pond?

For example, my airline goes underground for about 80 feet from the windmill to the pond. For that 80 feet, it's picking up some of the temperature from the ground at a 4" to 6" depth (can you tell I buried it by hand?). This means that in the Summer the delvered air is probably always a little cooler than the air temp. In the Winter the delivered air temp would be affected also, but with air temp (in Ohio) varying above and below freezing so much, the effect is more erratic.

Maybe the effects with 80' of line buried is minimal, but I bet it might be significant for the folks who are pushing air a few hundred feet underground from a compressor. Are there any Mechanical Engineers out there who payed more attention in Thermodynamics than this EE did who could outline some rules of thumb based on burial length and ground versus air temperature difference?

I'm certainly not an engineer but it would appear we are leaving out one important factor, that being the heat of compression.
The air entering the piping is already elavated above ambient due to that fact.

However I believe the temp of the air entering the pond from the compresor is insignificant relative to the temp in the pond unless the pond temp is already critical.

Don't frost lines in Ohio typically go deeper than 4 to 6 inches?

IMHO it's not the air that comes from the compressor that is of concern. It's the mixing of the deeper water with the surface air. In winter you can disrupt the relatively warmer water and replace it with cooler surface water which is not a good thing.

I would thing summer warming is not a problem unless you have a trout pond. In that case I only mix and aerate at night on really hot days. My phytoplankton bloom makes oxygen during the day anyway.

Theo - one of the numerous problems related to these topics. A big concern, for us that have frozen ground during winter, is heated air with water vapor entering the under ground air pipes causes water vapor to condense. Water in the pipe in frozen soil freezes the water in the dips/valleys of the airline and ice forms relatively soon to freeze a plug in the airline. Problems then occur.

During ice cover, and irregardless of the air temp in the pipe, when you bring water that is 39F from the pond bottom to the surface and expose this water to subfreezing temps this cools the water to less than 39F and redistributes it throughout the pond; depending. Water cooler than 39F puts additional stresses on your fish. Winter is the hardest season of the year on your fish. No use making this season even harder for them to endure buy reducing their living conditions to below 39F.

I think I see - Air temp going into the line does not have a big effect on the pond water temp, air temp at the surface of the boil (unaffected by ground temp OR temperature increase from compression) has a very large effect. Especially when the pond is froze over and the aeration free water hole is the only direct air-water interface. (All without Thermodynamics equations - very nice!)

The frost line is indeed a lot lower than 6" here. Water lines should be buried at least 3 feet down. I get surprisingly minor air flow stoppages from frost with the air line this shallow - two or three times a Winter, after a lot of rain when the temperature drops just right, airflow will stop for one to three days. I decided I could live with that, rather than trying to bury the line deeper or install a de-icer.

Hopefully Theo you have a pressure relief valve that operates when you have air blockages. If not mechanical damage will soon occur.