So you’ve just used muriatic acid (aka Hydrochloric Acid – HCL) for your pool and have some left over. What do you do with it after you’ve finished? Can you just put it down the drain?
This article will give you five ways on how best to dispose of Muriatic Acid safely, without harming you, your property or the environment.
If you have some leftover pool chlorine, we have an article on how to dispose of that too: How to Properly and Safely Dispose of Chlorine
1. Dispose of Muriatic Acid by Pouring It Into Your Pool
Muriatic acid is one chemical you’ll always need for your pool. Definitely don’t dispose of it by pouring it down the sink. Instead, store the acid in a cool, dry ventilated area in the plastic container it came in.
When pH levels are too high, use muriatic acid to lower the pH level and get it back down to 7.4-7.6.
2. Acid Wash Your Concrete with Muriatic Acid
Acid washing your concrete or your pool walls is another way to dispose of or use up leftover muriatic acid or hydrochloric acid. If you have stained pool walls or concrete, muriatic acid will remove it.
Simply mix the acid with 3 parts water and 1 part acid. When mixing, always pour the acid into the water and not the water into the acid – this is the safest way to avoid dangerous chemical reactions.
Now you can apply it to the concrete or pool wall, give it a scrub and after 10 minutes, wash it off with a pressure washer. Make sure you do a small test area first as it can leave the concrete with a rough finish. And never use it undiluted as this will badly pit the concrete.
3. Recycle Muriatic Acid
Most towns and cities have a Council Waste Disposal facility. Here they provide a safe way to get rid of muriatic acid and other household chemicals like bleach, chlorine etc.
They have the right equipment to handle hazardous chemicals and will process the chemical in a way that is the safest for the environment.
4. Pour Muriatic Acid Down the Sewer
Can dispose of muriatic acid (hydrochloric acid) down the sewer or drain?
In some states and towns, you can dispose of hydrochloric acid in the sewer or pour it down the drain. Before you do this, firstly check that your state or local municipality permits this. It may be illegal. And secondly, don’t pour full strength muriatic acid down a drain or sewer – it’s extremely hazardous.
In any case, you’ll need to water it down or preferably neutralize it before doing this to avoid damage to pipes and animals or plants. We have instructions on how to neutralize muriatic acid further in the article.
5. Use Leftover Muriatic Acid to Clean Your Toilet
Have some scale in your toilet? Instead of disposing of muriatic acid use the leftover acid to clean your toilet.
Here’s how. You’ll need to dilute it first. Most muriatic acid (also known as Hydrochloric Acid – HCL) for pools is diluted in different concentrations. A strength of 30-40% is common – you can check this on the label of the bottle.
Before using it to clean your toilet, dilute it further – 1 part acid to 10 parts water is good.
Now pour about half a cup of the diluted acid in your toilet and let it sit for 30 mins. to 3 hours. Flush the toilet and scrub the bowl. Much of the staining should come off.
6. Bonus Use: Use Leftover Muriatic Acid to Clean Your Pool Filter
Did you know you can use muriatic acid to deep clean your pool’s cartridge filter?
Firstly turn off your pool’s pump. With the pump off, release the pressure in your filter housing then open up the housing and remove the filter.
With the cartridge out, grab an old trash can (a plastic one, not metal) and fill it with water and muriatic acid in a ratio of 1 part acid to 20 parts water.
Soak the cartridges for an hour or so and rinse well. Now you have a super deep cleaned filter ready to be reinstalled.
How to Neutralize Muriatic Acid for Your Pool Safely
Another way to dispose of muriatic acid is by neutralizing it then pouring it down the sewer (first check with your municipal environmental department if it’s OK to do this).
Neutralizing muriatic acid is only suitable for small amounts. If you have gallons of it, you’ll need to use way too much neutralizer so it’s best to take it to your hazardous materials center for disposal or keep it for other uses around the house.
What You’ll Need to Neutralize Muriatic Acid
- Safety mask – do not breath in any vapors
- Long clothing to protect your arms and legs
- A wide mouth bucket
- Baking soda
- Access to water – make sure you have plenty
Muriatic Acid Disposal Safety Note: Muriatic Acid is highly corrosive; you do not want it coming into contact with your skin. It also releases a harmful hydrogen chloride vapor which you do not want to breathe in. This vapor can cause damage to your organs and respiratory tract, so please use appropriate protective gear.
Only do this in a well-ventilated area away from any heat and metal – this may cause a chemical reaction. And finally, keep children and pets well away from the area.
1. In a large bucket, mix one part baking soda to 10 parts water.
The amount of baking soda you need will depend on the volume of muriatic acid (hydrochloric acid) and the strength of the acid.
As a rough guide, you’ll need approximately 5.5lbs (2.5kg) per gallon (3.8l) of muriatic acid (for acid that is 30% strength). Check the label on the bottle for the strength.
2. Add the acid to the baking soda solution (up to 1/2 gallon/1.9l at a time).
Do this carefully and slowly. It will start to fizz which is normal. You must pour the acid into the water mix – don’t pour the water into the acid. And do it very slowly or it will overflow.
Wait for it to stop fizzing. This can take up to 5 mins.
3. Repeat – keep adding the acid to the baking soda solution until it stops fizzing.
If you add more of the baking soda mix and there is no fizzing, the muriatic acid is neutralized and safe to dispose of.
Side Note: People often ask “Will vinegar neutralize muriatic acid?”.
Vinegar will not neutralize muriatic acid. Vinegar is an acid and acids do not neutralize acids. The best case is that vinegar will dilute the muriatic acid but I wouldn’t recommend mixing the two unless you’re confident in your chemistry – mixing chemicals is dangerous if you don’t know what you’re doing.
Can You Dispose of Muriatic Acid Down the Drain?
Disposing of undiluted muriatic acid down the drain is not recommended. It can potentially melt plastic pipes and damage metal pipes. Professional Plumbers sometimes use it on blocked drains, however they know how to use it safely.
Here’s an example of what may happen if you pour undiluted muriatic acid down your drain. Imagine you poured some undiluted muriatic acid directly into your drain and it was blocked. The acid would just sit there.
The issue is if water is then poured on top of the acid. What could occur is an exothermic chemical reaction.
The reaction may result in the liquid ejecting violently from the drain and causing eye or skin damage. The chemical reaction could also release enough heat to potentially melt or damage your plastic pipes
So, in a nutshell, it’s best not to experiment with muriatic acid by pouring it down your drain, especially if you do not know exactly what you are doing.
Once your muriatic acid is properly neutralized, using the method explained above, you may then dispose of it safely down the drain flushing it with plenty of water – if your municipal authority allows this.
Will Muriatic Acid Eat Through Plastic?
Muriatic acid doesn’t eat through all plastics. Specific plastics such as ABS, polypropylene, polystyrene and polycarbonate are not suitable to store muriatic acid in according to Camlabs, a lab equipment supplier.
Are plastic containers safe to store muriatic acid in?
High density polyethylene and low density polyethylene containers are safe to store muriatic acid in. There. Plastic containers made from ABS or polypropylene are not safe to store muriatic acid in.
Plastic containers that are safe to store muriatic acid in are:
- Low Density Polyethylene (LDPE)
- High Density Polyethylene (HDPE)
- Polytetrafluoroethylene – Teflon® (PTFE)
When storing your acid in a plastic bottle ensure the lid is securely closed and that you label the container clearly. Keep it locked away in a cool, dark, dry and well-ventilated area.
How to dispose of empty muriatic acid containers
First you need to fill the empty muriatic acid container with water (only do this if you have used all the contents – you should never add water to large amounts of acid).
Now pour it into your pool. Usually muriatic acid is used to lower the pH, however if the bottle is pretty much empty, diluting what’s left will not have a noticeable effect.
Now it is safe to dispose of in the usual way (recycle it). Or you can choose to reuse the container once it is thoroughly cleaned using the method above.
An alternative is to neutralize the acid first. Add 90% water to the container with 10% baking soda and give it a good shake. Rinse the container thoroughly. Then dispose of it. Again, only do this if the container is empty.
Now you know how to safely dispose of your muriatic acid.
By using simple household items, you can neutralize the acid and dispose of it safely yourself. We also suggested some alternate cleaning ideas which may come in handy around the house.
Please take caution when handling the acid and if you are unsure about using any of the methods above, please take it to your local Council Hazardous Waste Centre for expert disposal.
Related Reading: Neutralize And Clean Up A Muriatic Acid Spill (Around A Pool)