General Question

kneesox's avatar

Will it kill the pipes if I pour boiling-hot liquid down the drain?

Asked by kneesox (4593points) January 12th, 2022

The bathroom sink and shower have been draining too slowly. I did the white vinegar and hot water thing in the sink and it helped a little.

I have a teakettle full of white vinegar that’s been at a bare simmer on the stove for two days, charming off the hard-water solids. There’s probably about a gallon. Is it safe to pour that down the shower drain, or will that destroy the pipes?

Or could I if I let it cool a little but still hot?

I’d like to unclog them without using Drano or calling a plumber if it’s something I can do. I’d just prefer not to kill the plumbing if I can help it.

The plumbing in that part of the house is about 35 years old.

Thank you.

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39 Answers

seawulf575's avatar

I guess it depends on what you are looking to clear in the way of a clog. Acid (vinegar) can attack the metal of the pipe. But the problem is that it would never touch the pipe…at least not in the house. Maybe farther down the line to the sewer. But to be honest acetic acid (vinegar) is a very mild acid and would likely not do much damage to the pipes.

But it may not do much for the clog either. What goes down your drain that you believe is clogging the pipes? If it is organic matter (hair, fats, etc) you are probably not putting the right product down the pipes. Bases work much better than acids for this application. That is why Drano works for it. Acid is good for removing calcium deposits and things like that (iron deposits, e.g.) But caustic helps dissolve organic matter better. So if you are trying to clean calcium or iron deposits off the pipes, the vinegar will do great. Other than that, I’d go with Drano.

Caravanfan's avatar

Bathroom sink is easy to fix. Underneath your sink is a PVC U-pipe. Dismantle that and clean it out and then reattach it. (I’m sure there are youtube videos to show you how. The shower is a bit tougher.

Tropical_Willie's avatar

Get a “hair snake” from plumbing supply place or big box hardware store.

RocketGuy's avatar

I would go with @Tropical and use a snake to physically remove the junk. Drano just dissolves the top layer, so is only a temporary solution.

Brian1946's avatar

I used to have that problem.

After I resolved it, I bought stainless steel drain strainers for my sink and my bathtub.

Response moderated (Spam)
kneesox's avatar

But the heat itself isn’t a problem?

Response moderated
Hawaii_Jake's avatar

I’m on mobile, so I can’t make a link look pretty. I suggest you try a drain snake. You can buy them at any big box retailer like Target.

Vastar 3 Pack 19.6 Inch Drain Snake Hair Drain Clog Remover Cleaning Tool

I’m sorry that doesn’t answer your exact question. I often pour boiling water down my sink without harm.

JLeslie's avatar

Not advised. The boiling water can be bad for the pipes, so it can be effective, but if you try it your should follow immediately with cooler water, and honestly I wouldn’t do it, but I know people who do.

The Liquid Plumr or Drano that is the FOAM works great for the sink. Read the directions. The foam keeps the chemical in all parts of the drain until you rinse it down with water. It only takes about 15 minutes if I remember correctly. It’s two chemical that you pour at once and it creates a foam.

Hawaii_Jake's avatar

I pour boiling water down the sink every time I cook pasta. No harm done.

janbb's avatar

@Hawaii_Jake Yeah – me too.

JLeslie's avatar

That’s a good point.

Edit: I googled out of curiosity. A lot of sites say what this plumbing company says. Of course, they are trying to sell their service. Worth a read about the different types of pipes though. Funny, they actually use the spaghetti example.

jca2's avatar

I had this problem and had asked a plumber at work, and he suggested the hair snake thing which is only about 3 or 4 dollars at Home Depot. It’s really disgusting what comes out of the drain. Even if you can use that and then use Drano, that’s another idea. Times I’ve used Drano or other declogger, I leave it in overnight and then put hot water in the morning, so it really has a chance to work its magic.

Brian1946's avatar

If your pipes are composed of:

Lead, they would melt at 621º.
Aluminum, 1,221º.
Copper-steel alloy, 1951º
Copper, 1,984º.
Cast iron, 2,060º-2,200º
Stainless steel, about 2,500º.

Boiling point water is 212º, so it poses no threat to your pipes.

Brian1946's avatar

Edit: Boiling point water….

JLeslie's avatar

^^Yeah, but what you left off was if they are PVC, over time there could be harm. I’d bet money I have PVC, because my house is built so recently. That probably why I had in my head it’s not good to pour lots of boiling water down the drain.

Dutchess_III's avatar

I always use bleach.

No. Boiling water won’t hurt your pipes.

kneesox's avatar

Thanks for the metallurgy data, @Brian1946, and everybody for the advice. I don’t worry about melting the pots on the stove either. What I was thinking was more like if the pipes are cold, would the boiling water crack or weaken them? And I was thinking of PVC too. I don’t know what’s down there.

I didn’t think about boiling water in the kitchen sink, and of course I do that all the time to. But would kitchen sinks be specced for that, different than showers?

Zaku's avatar

Why do people use PVC piping if it can’t handle boiling water, especially under a kitchen sink?

JLeslie's avatar

If you look at my link it talks about the joints of the PVC being especially vulnerable.

janbb's avatar

I just read a list of household tips that suggested pouring boiling water down the drain followed by baking soda or baking soda and vinegar to fix a clog so I guess it’s all right.

kneesox's avatar

Thanks for all the help. The pasta argument made sense, so I did go ahead and pour the hot vinegar down the drain. I think it helped some. The clog seems reduced. The temperature rating @jca2 found worries me a bit though. But I will go on and try the Liquid Plumr to see if that finishes the job. Opening the drain and clearing out the gunky junk is kind of a last resort.

JLeslie's avatar

^^Make sure it’s the foaming one. The others just run right down the drain and do nothing. I think it’s best if you do the chemicals when you haven’t used the sink for several hours and no water to dilute the chemicals if the clog is high up in the pipe.

You have to pour it all fast so the two liquids combine to foam. One liquid runs quickly while the other is thick and slow, so if you don’t dump it all out together they don’t combine as they should. Definitely read the directions. It’s actually very simple, I might have made it sound complicated.

kneesox's avatar

I tried the Liquid Plumr. It was just one liquid in a plastic bottle. I put half in the sink and half in the shower and followed it with hot water, including from a boiling teakettle. It helped a lot, but still not clear. I’m going to try a second application.

Thanks very much for the advice.

kneesox's avatar

@JLeslie, thanks, didn’t see that in the store. Direx say “pour the entire bottle down the drain”...doesn’t say anything about pouring two at once. So how do you control the mix?

JLeslie's avatar

@kneesox You pour everything so it all runs out together and mixes. The two chemicals react with each other and make the foam.

I have wondered if it’s best to put the stopper down so the two liquids would start mixing in the sink and then open the drain and the foam would eventually with gravity maybe run down? I’ve never tried that. The point of the foam is it doesn’t run quickly down the drain, it fills the pipe and sticks there so it eats away at all the garbage.

It seems to work well just pouring it with the drain open.

Edit: I just found this video of someone using it.

RocketGuy's avatar

@kneesox – the bottle has two compartments. When you pour, liquids from both compartments come out and combine in the drain. Then the foaming starts.

@JLeslie – if you stopper the drain, you will have to reach into the caustic foam to unstopper it.

kneesox's avatar

@RocketGuy, not if the drain mechanism involves a lifter and closer rod thing up behind the spigot.

Thanks for clarifying on the bottle. Is it an acid and base thing like baking soda and white vinegar?

Anyway, I tried to buy some today and there was nothing. The spaces on the shelves for Liquid Plumr were just empty. Also there has been no jugs of white vinegar in the stores lately. More weird supply chain stuff, I guess.

JLeslie's avatar

The foam is often hard to find even when stocking shelves isn’t an issue. I don’t know if stopping up the sink when pouring will possibly mean the foam doesn’t run down the pipe well and fill it up. Maybe that’s why they don’t do it that way. I haven’t tried it.

RocketGuy's avatar

@kneesox – I’m not sure about that. Regular Draino is very basic (NaOH) to be able to dissolve organic stuff. Adding an acid to create foam might reduce the effectiveness. There are probably other reactions that will create bubbles.

Ikara's avatar

If you have PVC (plastic pipes) then boiling water is a terrible idea. But if your pipes are metal then boiling water will not hurt them. Won’t unclog them either though

LadyMarissa's avatar

I don’t like using the harsh chemical product either. I kept seeing this idea on youtube & decided to try it. Put 3 tablespoons of Baking Soda down the drain. Follow that with about 1 cup vinegar. I pour the vinegar kinda slow so to keep it foaming. After the vinegar, wait about 10 minutes & pour some hot water (out of microwave) down the drain. The people of YT claim that will also unstop a drain, but that makes NO sense to me; however, it DOES work well with a slow drain. Since I’ve started doing this, I now only need to do it maybe once a year & my pipes stay running smooth. The first time I tried it, I been shopping in my local dollar store. Their store brand baking soda was 2/$1 & the vinegar was $2/bottle.So, I decided that for $3 that I had nothing to lose & I could clean it more than once IF necessary for the same $3!!! I could tell on the first use that I was going to like it. I don’t think using just plain vinegar would be as effective, but I could be wrong. The vinegar mixing with baking soda creates a foaming action that I’m assuming creates the right action to clean the pipes. Now every Spring when I do my Spring cleaning, I start with 3 TBSP Baking Soda followed by the vinegar in my kitchen sink, my bathroom sink, & the tub drain. I’ve also been known to throw some soda in the toilet followed by vinegar. Makes everything smell a bit better!!!

As an FYI, a quick search says that PVC pipes Melting temperatures range from 100°C (212°F) to 260°C (500°F) depending upon manufacture additives to the PVC. Water boils at 212°F, so technically speaking you could harm your pipes. Using the soda & vinegar method doesn’t keep the hot water in the pipes for long, so any damage should be minimized!!!

kneesox's avatar

Following up: The Liquid Plumr didn’t completely declog, but the drain almost returned to normal. I will get some more and try to finish it off. Thanks, everybody.

I did finally find some white vinegar by going to a Safeway in a part of town that has a different clientele, and I bought three gallons. Left two on the shelf. My regular supermarket still doesn’t have it and neither does Smart & Final.

JLeslie's avatar

Thanks for the update!

Years ago I was in Lowe’s or Home Depot and a plumber told me to buy probiotic granules for the pipes to keep them clean. I don’t know if it was only for septic? I never tried it. I googled and here is just one example:

I guess it eats away organic matter that creates clogs.

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