Acidizing a water heater?

[DWalt]

Several times in my life I have lived in areas where the water was very hard, and without having a water softener. In such circumstances, scale will build up inside the water heater tank over a period of years, to the point that the water cannot be heated properly so the hot water supply drops greatly, and you can hear a lot of rattling from inside the tank while the water is heating. My first experience with this was in a house I had in Midland TX in the late 1970s. At that time, Midland had extremely hard water. I had a neighbor who had this problem, and asked me about it. I told him that it was probably scale from the water. He had an electric heater, and what was happening was that scale would build up on the heating elements and eventually get thick enough to crack, with the scale fragments falling to the bottom. We pulled out his heater into the driveway and had a good look at it. It was full almost to the top with what looked like small seashells. He was going to replace it, but I suddenly had an idea - why not dissolve the scale with hydrochloric acid? We filled the tank with water and acid, and after several additions of concentrated HCl, the fizzing finally stopped. We flushed out a lot of fine silt, flushed it out thoroughly, and re-installed it. I have done essentially the same treatment (but without removing the tank) five times since in different homes, most recently early this week (the heater was installed six years ago). I started hearing a lot of rattling and the hot water supply had been greatly reduced. Fairly simple and quick to do. I just drained about 2/3ds of the water through the drain valve on the bottom (with the water off) and poured in two gallons of acid through the water line fittings on the top of the tank. I let it sit a couple of hours, then drained and flushed the tank thoroughly. Problem solved. The concentrated HCL is the same stuff used in swimming pools for pH control, and Home Depot sells it for about $6/gallon

I looked on the internet and could find no mention about anyone else ever having done this. Am I the only one which has performed this treatment, or has anyone else done it or something similar? Just curious.

 

[rwsmith]

That's pretty clever.....

I've never lived with hard water but I've never heard of this treatment. If it works, great! Maybe you invented something!

 

[Tinhack]

I've never tried it. I suppose as long as the glass lining is intact, it should work. I've been draining/flushing mine every year through the drain valve. I'm still wondering how you got the HCL into the tank. I've worked with HCL in plating and stripping but it still scares the bejeebers out of me. It is a very unforgiving strong acid. Every time I used it I was "suited up" in protective gear.

Have you tried using vinegar? It would take longer but it's a little safer.

 

[DWalt]

HCl is actually fairly benign to tissue, at least in comparison to nitric and sulfuric acids. Obviously, eye protection and great care should be used during the operation, but the worst part of working with HCl is the fumes. What I did was to dilute the concentrated HCl with water (50%) in a plastic bucket (acid into water, not vice-versa), then pour that solution through the threaded nipples at the top of the tank using a large funnel. That really reduces the fumes greatly. Obviously, you must disconnect the two (inlet and outlet) flexible water lines from the tank. Pour the acid through the funnel into one, the other side acts as a vent. Empty from the drain valve at the bottom using an attached water hose when all the fizzing completely stops. Reconnect the flexible lines, turn the water on, and let the tank flush with the bottom valve open. It would take a HUGE volume of Vinegar to do the job. Vinegar is only about 5% Acetic Acid. Concentrated HCl is about 37% HCl, and works much more rapidly than acetic acid as it ionizes completely. There's really little to fear from using HCL if you are careful. No way would I use nitric or sulfuric acids. By the way, HCl is not very corrosive to steel, although it does remove rust very well.

BTW - HCl is also a great toilet cleaner if diluted. Also works to dissolve scale in the upper ring, just pour some down through the flush tank riser. Works great to remove the scum from bathtubs and shower stall floors and walls. Sort of a miracle cleaner. It even works on plugged drains, much better than commercial drain cleaners. I have used it for those purposes for many years - but diluted, not concentrated.

 

[dave holl]

Where do you drain the acid/water mix? Assuming you have a 50gal tank, leave 1/3rd of the water, and add 2gal HCl, that means you are draining 16.7 + 2 = 18.7 gal of acid/water mix. If you have a sump in the basement, that mix will eventually find its way to a watershed. Can't be good downstream. I'm not a treehugger environmentalist, but I'd hate to be responsible for a fish kill.
Maybe that's why you don't hear of this more often.

 

[carpriver]

When I had my tankless water heater it came with a cleaning kit, a 5 gallon pale, a underwater pump, 2 hoses. You turn the power and gas off close the hot water out value and the cold in value. fill the bucket with white vinegar connect the hoses plug in the pump and let the vinegar run threw the heater for 2 hours do this for a couple of hours once a year or more often if you have lot of lime in the water (Hard water).

 

[bigwheelzip]

Where do you drain the acid/water mix? Assuming you have a 50gal tank, leave 1/3rd of the water, and add 2gal HCl, that means you are draining 16.7 + 2 = 18.7 gal of acid/water mix. If you have a sump in the basement, that mix will eventually find its way to a watershed. Can't be good downstream. I'm not a treehugger environmentalist, but I'd hate to be responsible for a fish kill.
Maybe that's why you don't hear of this more often.

I'd think the HCl is fairly neutral after it dissolved what was in the tank. Can always add some baking soda to the waste.

 

[Steve912]

A friend retired from AO Smith. He told me the glass liners were
broken before the heaters left the factory.

The intact anode(s) will protect the tank from ordinary corrosion, but I'd
wonder how much corrosion would occur from the acid?

 

[TX-Dennis]

I grew up in Midland and still live nearby. We still have very hard water. I just do what most folks in Midland do . . . replace the water heater every 8-10 years. I have seen the horrendous yellow vapor from a HCl spill. The building had to be evacuated for over an hour. None for me, please.

 

[RSBH44]

If diluted properly the acid will actually be nutralized from dissolving the lime scale. I used to use HCI to dissolve very bad lime scale build up in industrial coffee brewers. I have done electrical hot water heaters as well. Several years ago I discovered that 75% phosphoric acid works just as well but wasn't nearly a caustic and was somewhat safer than HCI. Proper eye protection, rubber gloves and a cloth respirator is still required when working with phosphoric acid. Especially indoors.

 

[muddocktor]

I did this on my Mom's water heater many years ago. The buildup had gotten as high as the lower heater element and was burning them out quickly. Her water heater was in a room that opened to the outside of the house and I went through a few gallons of HCL cleaning it out. It lasted many more years for her too after cleaning it.

And yes, the effluent coming out of the tank after it reacts is fairly close to neutral. That's why it gives such a big reaction to the calcium buildup inside the tank. But it sure is nasty pouring it into the tank and the fumes are just awful.

 

[dave holl]

I'd think the HCl is fairly neutral after it dissolved what was in the tank. Can always add some baking soda to the waste.

I didn't take that chemical reaction in to consideration Makes me feel better.
Dave

 

[JSR III]

I looked on the internet and could find no mention about anyone else ever having done this.

They all died!!!

 

[Skeet 028]

My FiL was a plumber/electician. Back in Md we had some pretty hard water. He used a product called Sizzle for tank and line cleaning. All it was, of course. was acid. So yeah..it has been done even on a commercial scale(pun intended). As far as the AO Smith guy..Fiber Glass is not all that easily broken. I doubt a water heater would last all that long with a broken liner. Sounds good anyway

 

[Steve912]

As far as the AO Smith guy..Fiber Glass is not all that easily broken. I doubt a water heater would last all that long with a broken liner. Sounds good anyway

Fiber glass?

No, tank lining is GLASS (unless you're thinking the tank is fiberglass--nope, just steel)...about as thick as a light bulb. If you ever flush your tank for sediment, you'll find pieces of it, among the scale.

The 'glass lining' isn't 100% anyway. Everywhere there's a penetration to tank (drain valve nipple, water in/out, pressure relief, anode), there's a ring of exposed steel tank.

If the glass lining was effective, you wouldn't need anodes, right?

 

[DWalt]

Where do you drain the acid/water mix? Assuming you have a 50gal tank, leave 1/3rd of the water, and add 2gal HCl, that means you are draining 16.7 + 2 = 18.7 gal of acid/water mix. If you have a sump in the basement, that mix will eventually find its way to a watershed. Can't be good downstream. I'm not a treehugger environmentalist, but I'd hate to be responsible for a fish kill.
Maybe that's why you don't hear of this more often.

Most of the acid is neutralized in the reaction with the scale in the tank, which is mainly calcium carbonate, at least where I live. I just run the depleted acid via a garden hose into the back yard, followed with a lot of water flushing. The soil here is quite basic, and any residual acidity would be neutralized. One treatment for highly basic soil is to put acid on it. Or Epsom salts.

 

[mtgianni]

Softeners are pretty cheap. My last one was under $400 and they go for a long time. My wife has skin problems but clothes last longer, food tastes better and your car has less spots when washed with soft water.

 

[DWalt]

One thing which will prolong the water heater's life and slow down scale formation is to keep the temperature setting as low as possible. I have always kept my water heater temperature setting at a level that is warm enough, if not slightly uncomfortable, in the shower with the hot water fully on. Also safer as it prevents scalding and uses less gas or electricity. There is really little reason to have it any warmer than you need to have a comfortable shower. With today's laundry detergents, you don't need extremely hot water for your washing machine.

The gas heater I replaced about six years ago was at least 19 years old, and possibly much older as it was in my house when I bought it in 1991. I acidized it twice for scale removal before it started leaking in 2010 and I had to replace it. But while I had the old heater, I always kept the temperature low.

I had a water softener once. It was a real PITA keeping salt in it, also it broke down at least once a year, and expensive for service.. I'd rather do without.

 

[chaparrito]

Our well water is very hard, but tastes great. I burn out a bottom element about once a year. The "seashells" get so packed in the bottom that it takes about 6 hours to drain the tank. Elements are cheap. I rigged up a piece of garden hose that attaches to my shop vac and I get in there through the bottom element hole and can suck out most of the scale, but not all. You can't flush it out the drain valve as it's too small. A fellow once suggested I take the original drain valve off and replace it with a brass ball valve, but when I look at that original valve it's made of cheap, fairly soft plastic and I'm not sure I could even get it unscrewed without potential damage, so I haven't done that yet. It's like a permanent 'to-do' item.

 

[mtgianni]

Our well water is very hard, but tastes great. I burn out a bottom element about once a year. The "seashells" get so packed in the bottom that it takes about 6 hours to drain the tank. Elements are cheap. I rigged up a piece of garden hose that attaches to my shop vac and I get in there through the bottom element hole and can suck out most of the scale, but not all. You can't flush it out the drain valve as it's too small. A fellow once suggested I take the original drain valve off and replace it with a brass ball valve, but when I look at that original valve it's made of cheap, fairly soft plastic and I'm not sure I could even get it unscrewed without potential damage, so I haven't done that yet. It's like a permanent 'to-do' item.

Most have a standard right hand thread then a small space and left hand threads. This keeps amateurs from unscrewing them.