How to Remove Rust From Plumbing Pipes

Posted on: March 21, 2022 by
Ian Scott.
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How to Remove Rust From Plumbing Pipes

How to Remove Rust From Plumbing Pipes

Rust on gutters, downpipes and steel rooves is easily noticed and can be attended to but when it comes to the pipes in your home, that channel water and gas it’s another matter. These days it’s common for PVC pipes to be used in plumbing systems for newly-built homes, replacing the galvanised iron pipes of old, but there are still plenty of these in older houses and other buildings. Copper pipes, used for the past 60 years in homes in Australia, are still used because they’re ideal for carrying water or gas. There’s virtually no sign of these copper pipes ageing. However, galvanised pipes are a different story. They rust on the inside, then eventually clog up.

You’ll get plenty of warning if your galvanised iron mains pipes are rusting because the water that channels through them comes out brown and tastes metallic. Although the rusty water is harmless, it is a warning that you’ll have to call a plumber and have the pipes replaced eventually, or cleared.

Of course, with gas pipes, you might not get a warning and leaks can be extremely dangerous. Gas can begin to leak through holes the size of a pinprick way before any corrosion is noticed and gas leaks can cause explosions.


What causes the pipes to rust?

When metals such as iron and steel corrode or break down, the result is rust, which is an iron oxide, usually red, formed by the redox reaction of oxygen and iron in water or moisture in the air. Galvanised pipes are manufactured from iron or steel and they’re then given a coat of molten zinc to prevent rust. But with age, the galvanising flakes off and the pipes rust, and the rust eventually eats through the metal.

But there are ways you can remove the rust from both the inside and outside your pipes and bring them back to functionality. It would be best done by a plumber, and before you try these steps, these are the items you will need:

  • Plastic Sheet or tarpaulin
  • Face mask
  • Safety goggles
  • Thick plastic/rubber gloves
  • Old toothbrush
  • Wire brush
  • Disposable cloths
  • Steel wool pad
  • Fine sandpaper
  • Paintbrush (optional)
  • Primer and paint (optional)
  • Naval Jelly

For the outside of the pipe

  1. Shut off the water at the mains and then place the pipe on asheet of tarpaulin. Using a wire brush scrub the surface as clean of rust as you can without brushing off too much metal with it. The more rust you remove, the thinner the pipe will become and could make it prone to cracking or it could burst under high water pressure.
  2. After you’ve brushed the pipe, use a fine grade sandpaper and rub in a circular motion over the pipe as an extra precaution to make sure it’s dry and clean and then wipe with a clean cloth.
  3. You will then use the rust-removing gel called Naval Jelly. (Apparently, Naval Jelly was used during World War II to remove rust from naval ships, hence the name).This product will dissolve rust, but make sure you use gloves to protect your hands. The gel is made of sulfuric acid, phosphate ester, phosphoric acid, isopropyl alcohol, polysaccharides, and water. This means that the gel can be dangerous if you don’t take the proper precautions. See the following:
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For Safety’s Sake

  • Naval Jelly is a highly hazardous and toxic product so it has to be kept away from children and pets.
  • The gel is also harmful to the environment so be sure to have a safe way of disposing of the waste – soda ash added to the gel will neutralise it.
  • Strictly follow all safety instructions on the gel container, and wear safety gear.
  • Naval Jelly should only be used in an area that is well-ventilated because the fumes are very harmful to your respiratory system.
  • Wash immediately with soap and water if any gel drops onto the skin.
  • If you somehow get the gel in your eyes, immediately flush with water and see your GP or go to Emergency.
  • If you swallow any gel, don’t try to vomit but drink plenty of water and go to an Emergency department immediately.
  • Do not use Naval Jelly on fibreglass, chrome, marble, cement, aluminium or plastic.

Apply Naval Jelly

  1. As mentioned, make sure you are wearing your safety equipment – gloves, safety glasses and face mask.
  2. With the paintbrush, apply a generous amount of Naval Jelly to the rust areas on the pipe and then use the toothbrush to get into any tiny crevices or joins.
  3. Make sure you leave the gel on for 10 but no more than 15 minutes during which time the gel will change the rust into a water-soluble paste. After 15 minutes you will cause pockmarks in the metal.
  4. With your clean, wet cloth, clean the gel from the pipe thoroughly. Then dry it with a clean dry cloth and check the pipe for any rust that might have been missed, if so, repeat the procedure.

Painting will protect the pipe

After you have brushed, wiped, sanded, applied Naval Jelly and washed and dried the pipe you can paint it to protect it from further rust if necessary.

  1. To avoid inhaling paint and primer, use a respirator and work in a well-ventilated area.
  2. Paint on a rust-inhibiting primer first, covering the entire pipe, even the areas that were not rusted, this will prevent a recurrence of rust on the whole pipe.
  3. Allow the primer to thoroughly dry, following the directions on the can.
  4. Paint the pipe.

Inside the pipe

  1. The first step is make sure the water is still shut off at the mains. This will obviously prevent your home and contents from being damaged by water.
  2. To clear the blockage in the pipe – as long as the rust hasn’t hardened – and if the blockage is accessible, try to prise out the pieces of rust with a steel pick.
  3. N.B. Don’t take the next step if the blockage is on a pipe that channels drinking water, gardening water or water used in preparing food. (If it is, you will need a plumber to replace the pipe or section of it)
  4. If the rust that’s causing the blockage is inaccessible you can use Calcium, Lime & Rust or CLR. Pour it down the pipe where it will soften the blockage and dissolve it, eventually, providing the pipe is horizontal. If the rust blockage is located at the knob, then spray the CLR and let it sit for a few minutes before washing it off with soapy water.
  5. When you have cleared the rust blockage, attach the pipe back to its original position, turn the water back on at the mains and open the tap. The water will be brown but let it run for a few minutes until it is clear.

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