Using 21 inch shotgun heat exchanger for condenser

[thomasedwin]

Some time ago I purchased a 21 inch copper shotgun style heat exchanger from a place called outdoor heating supply on ebay. It has a 1&1/2 inch copper tube with 7 smaller tubes inside, the 7 smaller tubes are connected by 3/4inch copper end fittings and then the 1&1/2 inch tube is the water jacket surrounding these smaller tubes. It is actually designed to be used as a heat exchanger for an outdoor boiler where boiler water or steam passes through a water jacket around 7 smaller copper tubes then potable water is run through these smaller tubes to exchange the heat. I saw this as a perfect setup for a condenser for my still because the 7 smaller copper tubes inside the jacket provides much more surface area to condense hot vapor when cold water is pumped through the surrounding jacket. In essences I'm using it as a hot vapor condenser instead of a heat exchanger. It works very well for this purpose and is very efficient only being 21 inches long. I have seen many other condenser setups that only have a single copper pipe inside another larger single copper pipe used for a condenser but they were much longer to provide more surface area to condense the hot vapors. Before I purchased this unit the seller said the manufacture says it is assembled using LEAD FREE SOLDER, I put my still together with this heat exchanger/condenser and have run a few batches and it works perfectly, Before running any actual product through this still I cleaned everything inside and out with a mix of white vinegar and lemon juice. On all the other solder joints on this still I used Oatey lead free silver solder. My first run, after removing the heads, produced a crystal clear product starting at 154 proof, the product was made from a whole wheat grain, white rice, cane sugar mash. It had a slight rummy taste but was otherwise good neutral drinking spirits. I'm getting ready to run my next 15 gallon batch as the fermenter bubbles are starting to slow down. As I started a pre-run hot water clean up on my still I noticed something odd, All the sweat solder joints on my still where I used the Oatey lead free silver solder have remained a white silvery color but the sweat solder joints on the heat exchanger/condenser that I purchased seem to have darkened to a grayish graphite color, I also notice this darker solder is much harder than the Oatey silver solder as in it is much harder to put a scratch in it with a sharp tool or nail. So far I have consumed about half a gallon or so of the product produced from this still with no ill effects, it seems very clean and gives no next day hangover. Here's my main question, What kind of solder could this be that was used on this Heat exchanger/condenser??? I'm getting a little paranoid that something could or might be leaching of this darker solder contaminating my product, Are there any long time Plumbers, brasers, welders, metallurgist out there that can set my mind at ease????? I'm all ears. Thanks TE.

[MG Thermal Consulting]

I can't help you out but like you, I'd wonder just because somebody says something, doesn't make it so! Without a UL label or ASME stamp, you have no certainty of anything, really.

[PeteB]

My reasonably educated assumption is that the silver solder in the shotgun has a lower % silver in it.

[Ursa Major]

Home Depot has a product called "Lead Chek." It's a pack of 5 swabs that have a chemical that reacts to lead. You just break the seal, swab the solder joints, and see if it changes color. Might be worth a try.

[HedgeBird]

I know I have used a solder on a still that turned dark in color in the past as well. I just tried digging though my collection of various solders to find this roll but no dice. When I started building stills I just used lead free plumbing solder, and then at some point I read that you should also avoid antimony. None of my local stores carried antimony free solder so I purchased about three rolls (various brand and melting points) on Amazon that where lead/antimony free. I know that zinc is sometimes used to create low melting temp solders and is said to be more susceptible to corrosion. I know I was specifically looking for high and low melting point solders at the time.

I doubt you have anything to worry about, but Ursa's suggestion might put your mind at ease.

[Falling Rock]

Use the lead check kit...but remember solid sterling silver tarnishes black!