So I'm looking at building my first immersion chiller and since I live in apartments hoses aren't always easy to come by and a pump may be easier in the long run. So I'm doing some sanity checks for myself on what pump to get.

The total amount of fittings you need to put together to fit onto a sink (more if its non regulation) comes out to a decent amount (priced from home depot).

Estimated pricing looking at the site for the wort chiller (1/2 build)

1/2" x 20' Copper Coil - $25.11

4 Right Angle Elbows - $0.68(x4)-2.72

5' of Rigid Pipe - $7.92

5/8" of clear tubing (10 feet) - $7.92

So I can probably get smaller lengths of the tubing so this is about $40 for this setup.

An addition of all the fittings needed to get it work with kitchen sink adds on a good $20+ minimum.

Estimated head losses on this against gallons per minute using the D-W equation, so I'm skipping using reynolds number and simplifying the calculations

.25*0.2083(100/140)^(1.852)*(x)^(1.582)/(1/2)^(4.8655)+.08*0.2083*(100/130)^(1.852)*(x)^(1.582)/(5/8)^4.8655

=91.5*x^(1.582) and x is in gallons/minute

+20% for fittings etc.

=1.10*X^(1.582)

So with a 250 GPH pump (at the head this is given)

1.10*(250/60)^(1.582) I can assume 10.5 feet of head loss.

Anyhow, thats pretty good as using 3/8" diameter increases this to 41 feet of head loss and 1/4" to 300 feet. This obviously doesn't count losses at the water heats up.

To maintain an effective heat transfer simplify it down to you want 4 feet per second, as swirling the water maybe gets the speed to 4 ft/s at the edges. (total BS numbers). But basically the line will be cleared of water within 2 seconds. Your standard city garden hose runs at 10 GPM which is similar and should give 4 feet per second. (Your inner house faucet maybe gives 3 GpM)

So estimating the power of the pump I need (at minimum) to maintain 10 gallons/minute (yes I know the density is higher in the wort, just keeping it simple for now).

(10 gallons/minute)*(62.4 lb/ft^3)*(32.2 ft/s^2)*(42 feet)=

80 Watts

if I want to double the flow rate

471 Watts

Half the flow rate

13.2 Watts

So ideally I want a pump somewhere in this range, that garden hose is 10 GPM at the tap supposed, which may be a lot less after it reaches your tube.

Also assume a bad efficiency if you're looking at voltage*amp draw instead of the pumps actual horsepower something like 0.6 which will increase these numbers to 133,785 Watts, and 22 respectively.

So back to the final retail pump selection, my original inclination was a bilge pump, but that requires DC. So rather than worrying about dealing with AC/DC wall worts or transformers or a car battery just look straight to AC.

A fountain pump seems like a pretty simple option, I'm just trying to find the right one. A fountain pump usually includes a flow rate at a head. (600 gallons/hour for a 15 foot high fountain etc.)

http://www.amazon.com/Beckett-7107910-Pond-Waterfall-600gph/dp/B000MRSU76/ref=sr_1_7?s=garden&ie=UTF8&qid=1306201338&sr=1-7

At 600 GPH at 16 foot height

Is a 32 Watt pump (at flow), so just guessing now since I'm feeling lazy thats about 6 GpM on the chiller, and 2.5 ft/s flowrate so it'll take about 15 seconds to return through the system

Now a utility pump looks like it may be more bang for your buck

http://www.amazon.com/Wayne-RUP160-6-Horsepower-Oilless-Submersible/dp/B0009X8O2E/ref=sr_1_8?ie=UTF8&qid=1306201883&sr=8-8

But the max head is 20 feet, much less than what the horsepower can send through it. You can see the pattern between the two here (for a similar pump)

If I plot my function 1.10*X^(1.582) against that, where they intersect is basically where it'll operate at. Which on that graph is only about 6 Gpm again

Anyhow, I need a pump recommendation, or am I shooting for way too high flowrates? Would 3 GpM be more reasonable?