Corrosion of tube flares

Question

Dear Dr. Brew,

I'm new to BUNN coffee makers and bought a used CWTF-35 made in 2002. Upon set-up I noticed a water leak and traced it to the water coil fittings at the tank bulkhead. Taking the flare fittings loose, I found that the copper flares had nearly completely disappeared where they contacted the stainless steel elbows, and that is where the leaks were coming from. This was found on both of the stainless steel elbow/copper tubing flair interfaces. The flared fittings at the other ends of the copper tubes, where they joined brass fittings were in perfect order.

It appears that a galvanic corrosion process caused the copper to fail at the stainless steel contact point on the elbows. Since this was only a 7 year old machine, and appeared to have seen little use, I am puzzled. I'm a mechanical engineer, so I am familiar with dissimilar metal galvanic corrosion problems, but usually they involve ordinary steel and aluminum. I am considering replacing the stainless steel fittings with brass fittings to prevent future leaks. Is this a problem that is typical of BUNN machines? I don't want to have to re-plumb the machine with new copper lines every 5 years or so.

v/r,
Gary

Answer

Dear Gary,

Thank you for your E-mail. We'll try to help with the issues that you mentioned below. To begin, the fittings and nuts are brass, either nickel or tin plated. They are not SST. If they are SST, then someone changed them without using BUNN parts.

We are not too sure why the copper flares have disappeared. As this was a used machine, it may be that someone cleaned the machine with the wrong cleaner or disassembled the parts and then cleaned them in a cleaner that is aggressive toward copper. It may be also that the parts were re-assembled and over-tightened by quite a bit, therefore thinning the copper down. It is just very difficult to determine without knowing more of the history of the service of the machine. It is also unknown why the machine was sold used, perhaps it was due to an issue as mentioned above.

We have used these parts and materials in combination for many, many years and just do not have a field issues with them. SST, tin, nickel and copper are fairly close to each other on the galvanic tables.

Hopefully you will have many years of good service from your BUNN coffee brewer.

Happy Brewing,
Dr. Brew

Number of cycles during pulse brew

Question

Hello Dr. Brew,

We're a new coffee shop in Quebec City, Canada, and are proud to be equipped with a Twin BUNN ICB brewer as well as a BUNN MHG grinder. We had a little trouble setting all this up but everything goes fine since we began to use a water pressure regulator. No more surprises with TDS variations! We use an Excel spreadsheet kindly provided to us by Vince Fedele from Terroir Coffee and which was written by you originally, I think.

The only thing I still don't understand is the number of cycles during pulse-brewing. Is it a number hard-set on the brewer or a result of a formula involving other parameters? Your help would be greatly appreciated!

And congratulations for achieving such innovations as pulse brewing and pre-infusion delays. Good coffee truly deserves a proper brewing for achieving wine-like character and complexity!

If you ever get by Quebec City, we'll be honoured to serve you the best cup of coffee in town!

Constantin Ioan

Café Le Nektar
Quebec, Canada

Answer

Dear Constantin,

Good to hear from our friends to the North. The ICB brewer you have can be set to pulse brew in one of two alternate ways. You can select EasyPulse or the Manual mode. EasyPulse is a predetermined routine consisting of an Initial ON period (15% of the original time) followed by seven OFF and ON cycles till the selected volume is acheived.

Happy Brewing,
Dr. Brew

Water Heater quality

Question

Dear Dr. Brew,

I have heard that I should not use water from my hot water faucet, i.e. from the household water heater line, but should always use the cold water line as a source. Is that due to temperature, quality, or something else? Does not the BUNN keep and hold hot water pretty much as a house water heater would? Thanks for any info.

Ken

Answer

Dear Ken,

I have heard the same information concerning the use of water from a water heater system.
A home water heater is usualy set at 140°F or lower. A commercial and some home brewers maintain a ready to brew temperature of 195 - 205°F. A water heater system is held at supply line pressure hwere a coffee brewer is vented to atmosphere.

I went to the EPA web site to ask for information and received the following.

Recently you requested personal assistance from our on-line support center. Below is a summary of your request and our response. Thank you for allowing us to be of service to you.

Dr.Brew - Are there reasons why you should not consume water from a water heater system?

[Thank you for your inquiry to the EPA Web site. Your request has been received by the Headquarters Public Access Service, a contractor operated reference and referral service.
You asked if there are reasons why water from a water heater system should not be consumed. We have not been able to locate any information on this topic on EPA's Web site. The Safe Drinking Water Hotline provides information about EPA's drinking water regulations and other related drinking water and ground water topics. Safe Drinking Water Hotline staff can be contacted by:Telephone: Toll-Free: 1-800-426-4791 Local (Washington, DC metro area) and international calls: (703) 412-3330 Address: Safe Drinking Water Hotline (4606M) 1200 Pennsylvania Avenue, N.W. Washington, DC 20460The Office of Ground Water and Drinking Water (OGWDW), together with states, tribes, and its many partners, protects public health by ensuring safe drinking water and protecting ground water. OGWDW, along with EPA's ten regional drinking water programs, oversees implementation of the Safe Drinking Water Act, which is the national law safeguarding tap water in America.The Office of Ground Water and Drinking Water (OGWDW)’s web page is located at: http://www.epa.gov/safewater/index.html_This office can be reached by: Phone: 202-564-3750 Fax: 202-564-3753Find an answer or ask a question: http://safewater.custhelp.com/cgi-bin/safewater.cfg/php/enduser/std_alp.php_Address: Office of Ground Water and Drinking Water (4601) Ariel Rios Building 1200 Pennsylvania Avenue, NW Washington, DC 20460-0003Thank you. Public Access Service, operated by ASRC Management ServicesEPA Headquarters Ariel Rios Building1200 Pennsylvania Avenue, N.W. (3404T)Washington, DC 20460Fax: (202) 566-0574

Each manufacture generally states in the installation manual, whether the equipment should be plumbed to a cold (tap) water supply or hot water (with a specified maximum temperature) supply.
Also review all supplied literature for water filtration systems.


Happy Brewing,
Dr. Brew

Brew temperature

Question

Dear Dr Brew,
Does the BUNN Home Brewer heat to a consistent 200 degrees all the way through the brew for proper extraction? Let me know, I would like to recommend it if it does, and get one for myself. Or, if you know how I can get properly extracted coffee at home, let me know.

Thanks so much

Bruce
Owner
Olson Coffee Roasters Inc

Answer

Dear Bruce,

The ideal temperature range for brewing coffee with the drip method is 195 - 205 degrees Fahrenheit. BUNN home units are designed to maintain brew temperature within this range.

The most critical phase of the brew cycle is the beginning and middle portion for brew temperature. Check out a previous response to see the brew phases. The Specialty Coffee Association of America (SCAA) recommends the temperature in the basket stays within the temperature range mentioned above during normal operation for at least 90% of the contact time between the water and the coffee grounds. The water contact temperature is measured in the center of the filter on the surface of the coffee.

I prefer to place a thermal couple in a spray head opening when measuring temperature of the brew water. This removes the variable of how the ground coffee was stored (some keep their coffee in the freezer or refrigerator).

Happy Brewing,
Dr. Brew

Temperature concerns

Question

Dear Dr. Brew,

Hope you are well. We are contacting you to know if there’s a possibility in a ... U3 to adjust the temperature of the coffee without take off the quality of the coffee. We know that it has a thermostat that can be adjust(ed), but we need to know if there is a another possibility to do it.
Thanks for your help.

Jorge Solano

Answer

Jorge,

The brewed coffee in this type of unit is maintained by the heated water in the main tank that surrounds the coffee reservoir. The holding temperature can not be reduced without altering the brew temperature. Normal brew temperature is 195-205o F (92 - 96o C). I suggest checking the temperature of the water reservoir and reducing it to the lower end of the range. Brew a sample coffee to assure that you still have a brew that meets your taste profile.

Happy Brewing,

Dr. Brew

Bad taste

Question

Dear Dr. Brew,

I have a small coffee shop. We have a brewer that has the most horrible taste in it. We have other things hooked up to the water source and have no problems with that, however the BUNN brewer (plumbed in to the water source) from both the water valve, and the coffee brewer taste awful.

This machine sat for a while and I have run numerous batches of coffee and fresh water through it, but I can't get rid of this taste. Is there something I missed when cleaning it and hooking it up? Advice would be greatly appreciated.

Deanna

Answer

Deanna,

It's hard to say what may have happened while the unit was stored. I would suggest taking the unit to an authorized service center. They will be able to dissasemble the unit and clean the tank. You may ask them to examine and clean the internal plumbing lines as well. I am not sure if the unit was stored with water remaining in the tank. I would suggest always draining the unit before storage.

Happy Brewing,
Dr. Brew

Dilemma with decaf

Question

Dear Dr. Brew,

We have a customer with a BUNN Dual Soft Heat brewer and interface G9 grinder. They recently switched from using a Swiss Water Decaf coffee to a Natural Decaf. However, the grounds are now overflowing the filter when we brew the Natural Decaf (either side). We don't wish to coarsen the grind and alter the regular coffee, so we tried an -078 sprayhead and lowered the throw, but it's not an ideal solution. I know with a more advanced digital brewer we could program pre-wetting and extend the pulse, but what is the workaround with this wonderful analog Soft Heat brewer?

The water here is very hard, and the customer has a softener, and we also use a BUNN Taste/Odor/Lime filter for the brewer. The brew water shows 7 grains of hardness on my test strip. I welcome your suggestions!

Mike
Leelanau
Coffee Roasting Company

Answer

Dear Michael,

Brewing decaffeinated coffee has always been a challenge compared to the regular counterpart. Adding a water softener only increases the annoyance of long brew cycle times and no filter margin or overflow of grounds in the funnel. You mention the "brew water" measuring 7 grains of hardness (1 grain = 17.1 mg/L or PPM). Is this after the water treatment systems or from the main water supply? Is the overflow only occurring on the largest batch size or does it happen for all three volumes?

You mentioned changing to a slower flow rate spray head and reduced weight -- did you maintain your water-to-coffee weight ratio? I need to do some research from my end to understand the effects of softened water and using a lime sequestering filtration system together. As you can tell, this time I have more questions than you.

To Be Continued

Happy Brewing,
Dr. Brew