DIY Water Heater Calcium Removal—Avoid 3 Costly Mistakes!


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The buildup of limescale deposits can cause water heater failure. White vinegar or descaling solutions are the safest way to remove calcium deposits from a water heater. Using strong acids or attempting to scrape out deposits can damage the water heater.

I recently saw a YouTube video clip that showed a guy getting calcium deposits out from his electric water heater using a wet/dry vac. In the video, one of the tools the guy was using to scrape the calcium off the bottom of the heater before his vacuum sucked it out was an evil-looking meat hook. I had my doubts about the advisability of that, so I asked a friend who’s a veteran plumber. His answer? “Do me a favor… DON’T!”

If scraping out calcium deposits is a bad idea, how do you deal with them? And why should you care, anyway?

Most common causes of water heater failure arise from ‘calcium deposits’ or ‘limescale’, consisting of calcium carbonate mixed with other minerals. These deposits accumulate on the water heater floor, heating elements and anode rod over time, leading to reduced heating efficiency and safety hazards.

Should you worry about limescale in your water heater? What’s wrong with using a meat hook to scrape it out? Is there anything else you should know before you tackle calcium deposits? Let’s find out.

The Most Common Cause of Water Heater Failure and What To Do About It

If your water heater is over five to six years old, the chances are that it’s already growing sluggish because of accumulating calcium deposits. If you’ve been noticing any of the following symptoms, then a build-up of calcium deposits in your water heater is the most likely cause:

  • having to wait a long time before the water heats up
  • getting lukewarm water, or the hot water running out too quicky
  • the water has a funny smell to it
  • the water is brownish or yellowish
  • hearing strange, banging noises from inside the water heater 

Getting rid of the limescale build-up in your water heater will very probably solve these problems. (If you find that your water heater’s heating element is already damaged by limescale building up, this helpful guide will show you how to replace it cheaply.)

Removing calcium deposits isn’t necessarily hard to do. There are a bunch of descaling solutions available on Amazon, like Flow-Aide, Hercules or QwikDescaler+. (I’ve tried Hercules, and it works well.)

Hercules 35235 Haymaker Tankless Water Heater Descaler Kit with Pump and Hoses, 32 oz.
  • TANKLESS WATER HEATER DESCALER KIT: Includes one 32 oz. bottle of Haymaker solution, two 5' hoses with 3/4" NPT fittings, one 550 GPH electric re-circulation pump with 25' power cord, and one 3.5...
  • DISSOLVES MINERAL DEPOSITS: Quickly and easily dissolves carbonates, sulfates, phosphates, rust, oxides and other inorganic deposits that restrict flow to restore circulation and heat transfer...
  • CITRIC ACID BASED FORMULA: Citric acid based, solvent-free, and VOC-free formula is 3 times as effective on scale as vinegar and has no foul odor
  • NON-CORROSIVE AND SEPTIC-SAFE: Compatible with most common plumbing materials including metals, rubber, steel, PVC, CPVC, and ABS, and it is also non-corrosive and safe for septic systems, sewers, and...

Besides these ready-to-use products, you could make up your own solution; diluting a strong acid like muriatic or sulfuric acid would likely make for a quicker, more powerful clean, but a safer, slower option would be a solution of plain old white vinegar.

Once you’ve allowed your water heater to ‘sit’ with the descaling solution in it for the amount of time recommended by the descalant manufacturer, you would simply flush it out, following the method described in this post (which, by the way, also describes how to cut down your water heater’s electricity bill to save $$$, so it’s definitely worth checking out.)

Some manufacturers of water heaters have brought out self-cleaning units, which are theoretically supposed to prevent lime-scale build-up and help you avoid having to remove the calcium deposits in the first place. However, they are not always effective.

What Could Go Wrong While Removing Limescale?

If descaling my hot water heater is so simple, then what’s the problem? What could go wrong?

Well, though it’s a simple enough process, it pays to take certain precautions, and to make sure that you don’t make mistakes that could end up costing you a packet of money. 

For a start, keep in mind that with the exception of vinegar, you’re dealing with strong and potentially hazardous chemicals. Treat all descaling solutions with due care, no matter if they’re store-bought or mixed at home. Kit yourself out in basic safety gear – rubber gloves for your hands, a face shield to keep fumes and spatter out of your face and eyes, and ideally, a pair of sturdy overalls and boots to make sure that no strong chemicals get onto your clothes or skin.

Three Serious Mistakes to Avoid

Here’s a handy list of dos and don’ts that’ll help you steer clear of mistakes that could turn out to be very expensive:

1. Don’t Think, ‘Stronger is Better’

When you’re dealing with corrosive acids and chemicals, you can’t simply bung in more of the stuff, expecting it’ll do a better job. The solution could eat away at the insides of your water heater and permanently damage it; this is called ‘etching’.

Etching is especially likely if you’re using sulfuric or muriatic acid, which can be dangerously corrosive to stainless steel. (Muriatic acid is a form of hydrochloric acid or HCl, typically diluted to less than 30% concentration.) Even if using a standard descaling solution, read the instructions to learn how to dilute it before application.

If you’re mixing your own solution, there’s no standard for exactly how much water to add to dilute inorganic acids for descaling purposes. However, you’d be safer mixing a more dilute solution at first, and strengthening it a little if needed. 

Organic acids like vinegar (acetic acid), citric or oxalic acid are gentler on your water heater, but are more expensive compared to inorganic ones like muriatic acid.

2. ‘Longer is Better’ Doesn’t Work, Either

If using a store-bought descaling solution, read and follow the instructions on how long to let the water heater ‘sit’ before you flush it out. If you’ve mixed your own, play it cautiously, and give it only a few hours, say three to four hours, before you drain the water heater. The exception is if you’re doing a vinegar flush, where it’s safe to let it work on the insides of the heater for several hours (between 12 and 24). 

3. Don’t Just “Scrape it All Out”

As I shared with you right at the beginning of this article, experienced plumbers caution against scraping out calcium deposits. Why’s that? Well, the inner tank of your water heater is typically made of stainless steel that has a glazed or vitrified coat to it. The glaze protects the steel itself from being eaten away by the minerals in the water coming into the heater.

When you scrape away at the sides or bottom of the water heater’s inner tank using a sharp object like a meat hook or a metal coat hanger, you’re very likely damaging the glazing and exposing the steel of the water heater tank to faster corrosion and future scale build-up.

If you’ve read all the way to here, removing limescale (calcium deposit) build-up from your electric water heater should be a breeze for you. So, go on and get started!

Calcium deposits can also build up in your pipes and cause vibrations and noises.

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