De-scaling heat exchanger

spclark

I'm looking for recommendations: I have a heating system in my home that has a hot water heater powered by a heat exchanger, which I have good reason to believe has built up a layer of lime (like a tea kettle or boiler tubes) considerably reducing its efficiency.The water heater itself is lined with polyethylene; the heat exchanger coil is probably copper tubing. I understand the general principle for removing the lime build-up involves introducing a lime-dissolving solution (I've used dilute hydrochloric acid before for similar operations on stuff I can hold in my suitably-gloved hands) into the tank, after shutting off the cold water feed & draining the hot water out, then removing the overflow/safety valve.As this is my home water supply heater I'm reluctant to use hydrochloric acid for fear of damaging the copper tubing. Have any of you list-watchers out there had experience with this kind of thing before?The system is by Amana, I believe Raytheon provides the hot water tank / heat exchanger unit. The service people I use for the entire system have offered to do this operation for me but, though I was told they'd call to set up an appointment, I have yet to hear back from them. I feel well capable of doing the work myself but need a bit of advice on what product to use to dissolve the lime safely.

Lowrider

We do this same maintenance operation annually to the boiler in the wastewater treatment plant I run. We used to use a product called LimeAway. This stuff should be mixed in a 50/50 solution with water. Problem is, it costs 20 - 25 bucks per gallon and we used a lot of it.We now use concentrated phosphoric acid (that's all LimeAway was anyhow). We mix 75% phosphoric acid in about a 6/1 (six parts water to one part acid) solution, add just a small amount of detergent for a surfactant, and it works like a dream. Won't harm the metal and completely dissolves the lime scale.Wear rubber gloves. The solution comes out in the 1 - 1.5 pH range. Not good for your skin.If you don't need much volume, the LimeAway is probably the best way to go. It's available commercially. I've even seen it in WalMart stores.

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She was only a fisherman's daughter,But when she saw my rod she reeled.

turbo

SPClarkTry vinegar, it is an excellent descaler, and very cheap 70 cents a gallon, if you pour it in full strength and use a little heat for twenty four hours, it will flush out and leave system like new. Dispose of residue, in a responsible way, I'm sure you could flush down you sewer system without any problems, but check it out.

spclark

Thanks Turbo & Lowrider,LimeAway - use it myself; I considered that, save for the fact that the coil needing descaling is about 12" tall. I think I'd need about 7 to 10 gallons (full-strength) to do a quickish job. Maybe a 1:8 or 1:16 solution would work, over time.The vinegar thing'd work too, except for the time thing; we'd be out of hot water for the duration of the treatment & clean-up. The vinegar though has the edge for bio-degradeability over the LimeAway. I have a septic & would rather just drain the "remains" onto my gravel driveway; most of it's limestone gravel & would quickly neutralize the vinegar.

wundudnee

Hydrochloric acid is just lab grade muriatic acid. Neither one should harm copper. Plumbing supply houses sell several products by brand name that are basically HCL or muriatic. One is called sizzle and takes off all rust, calcium and magnesium scale without harming copper. Nitric acid will take off a layer of copper or brass until it is completely gone, but I've never had muriatic hurt copper. Take a small piece of copper pipe and soak it awhile, I don't think you will see anything damaged.

Pelican

To descale a mullet I use a kitchen knife.

218Beekeep

Pelican,it works on snook too.

spclark

Wundudnee,Thanks for the info; I'd I hunch muriatic would work. I've heard its used for taking the lime out of water pipes (old, shallow wells for instance) made of steel. Used some last year to take the crust off of a friend's plastic fish pond after she brought the critter's inside to their winter pasture.Pelican & 218Beekeep - we're talkin' dimestore "carp" here (the orange kind), nothing worth scaling....

YODA

YOU MAY WANT TO INSTALL A ITEM CALLED A LIME BUSTER, WE INSTALL THEM ON ALL THE HOT WATER HEATERS AND BOILERS WE PUT IN. THEY SAY THAT THE BUSTER WILL KEEP THE LIME FROM COLLECTING IN THE COILS AND CONNECTED PIPE'S,IT ATTACHES AT THE POINT WHERE THE HOT WATER COMES OUT OF THE WATER HEATING DEVICE.

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WARNING MINES BIGGER & HOLDS MORE AMMO

spclark

Yoda,Thanks for the info. There IS a factory-recommended device on the cold water infeed to the water heater that slowly feeds food-grade phosphate into the cold water, supposedly to prevent the lime build-up. I have to assume it's been working all these years - the system was installed in (I think) 1984 or '85 & with my well water (over 440 grains hardness, untreated) & I've had no problems so far. The intended de-scaling operation is merely preventive maintenance at this point; the heating solution circulating thru the coil doesn't have the recommended temperature differential between the hot and cold side so I'm afraid the burner unit could work too hard & overheat. Besides it wastes natural gas running longer than needed.

sealyon

You might try Iron-Out. Used it on my hot water heater with good results. Can usually find it at most hardwares............

turbo

Another suggestion; the anodizing rods which prevent lime build up in hot water heaters dissolve with time and must be replaced, depending how hard your water is depends how long they last.If, your system is a closed system, what would really work well, would be using de-mineralized water.Ideally this would solve all your problems.

spclark

Took the beast by the tail yesterday; found a product at the grocery store (called LCR - on the shelf next to LimeAway - active ingredient monocarbamide hydrochloride) for about $4.00/quart.Took about four hours, start to finish. Set up a bucket at the tank drain with a pond pump & hose to recirculate the 10 gallons of diluted solution. Flushed the residue off with repeated blast of cold water from the tank infeed line (at the bottom, feeds the drain input). Thanks to all for your input. Anyone want more info feel free to ask.SPC