Re: [compost_tea] Air pump selection

From: Robert Norsen <bnbrew_at_yahoo.com>
Date: Thu, 2 Oct 2003 08:14:01 -0700 (PDT)

Yes David That is not how I would do it but that should work if there is NO back pressue going into the bag. But using the bag volume as a measure is I think not very accurate. Bags volum stops where? top open or tp clsed with 1" of matarial or less or more?? Of course if the pump exceeds the bag volume in 1 munute there are always fractions of 1 minute and a trace of math. Bob

David Loring <dloring3_at_cox.net> wrote:Robert - I suppose a funnel over the air stone and a short pipe to the surface would do it. I was just trying to caution people not to assume any pump they buy would not be affected by the pressure of water, even in a 5 gallon bucket. I know it is not a lot (1 psi will push air down through 2 feet of water) but it is worth noting if you're using low cost pumps. Given, even cheap aquarium pumps are probably designed to push water down a few feet. I just didn't want anyone to be surprised if no air came out of the bottom of their pipe.
 
Dave
----- Original Message -----
From: Robert Norsen
To: compost_tea_at_yahoogroups.com
Sent: Tuesday, September 30, 2003 11:35 PM
Subject: Re: [compost_tea] Air pump selection


David you calculate the back pressure at any depth and calculate the result. If you want to measure actual rate of flow at depth, release water at the intended depth but collect it at the surace. Easily done. I will let you figure our how. X.
David Loring <dloring3_at_cox.net> wrote: There are pumps and there are pumps. For instance, the air pump that comes with the KIS 5gal brewer is fine for a 5 gallon bucket but it loses air volume quickly with increased pressure due to depth. My large Alita pump is less affected. I'm not real familiar with aquarium pumps but think most small ones are diaphram type and thus perhaps OK. Try blowing up the same bag in the bottom of a 5 gallon pail filled with water and see if you get the same result, at least that's one way to test it under some pressure.
 
Dave
----- Original Message -----
From: Robert Norsen
To: compost_tea_at_yahoogroups.com
Sent: Tuesday, September 30, 2003 6:27 PM
Subject: Re: [compost_tea] Air pump selection


Kirk and other would -be home brewer builders - One problem of procuring air pumps is that the pump ratings are not very reliable. At the shallow depth of the small brewers you can assume free air. No back pressure. To measure actual air delivered assemble your entire system including the diffuser you will use. Insert in a totally air evacuated plastic kitchen trash bag. Tape this and other openings of the bag securely so NO air can escape. Operate the pump for 1 minute. The bag will normally be partly filled. Instantly seal the air from escaping via the pump or other escape routes. Gently insert the bag into a rectangular box so you can take normal inch measures.
 
Inches cube divided by 1728 will give you CFM. The smallest CFM I use for 5 or more gallons is 1.7 measured this way. The pump is rated at 0.7 cfm! I have measured other .7cfm pumps that measured this way only .4 amd .28 cfm.
 
In operation the amount of air available has everything to do with the compost, temperature and nutrients that your brewer can handle in an aerobic condition. The gallons of the brewer has little effect. In other words you can have a 5 or a 15 g brewer with the same air if you use the same load of 'stuff'. The ACT will be somewhat less concentrated at 15 g but the total product is often double in the larger quantity even using the same compost and nutrients. That surprised me, too.
 
Another out for your small home built - You can add another aerator system along with the basic system to increase the capacity of your brewer, put the small brewer in a larger tank with increased compost and nutrients. So the day you want more ACT you can brew it for just the trouble of added pump and aeration system.
 
GOOD aquarium pumps are not cheese or unreliable. They are made to go for years at a time,, 24 hours every day and SOOOO quiet they don't bug you or your sleepy time pal. They use the amount of current of a small light bulb. Cost? less than $ 75.00
 
Just don't ask my name. X . . .

Kirk Leonard <kirk_at_oregonatural.com> wrote:
Goshdarnit, I messed up some numbers again, I think. 3000 cc's is about 183
cubic inches, .11cfm. Sorry. At .02cfm per gallon of water, still not
enough for 5 gals tea needing more than ambient oxygen, imo. Somebody
better with these numbers or a better idea what air/water volumes should be
should correct me.










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Received on Thu Oct 02 2003 - 12:39:29 EDT

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