Using One Shot drain clearer in sinks

Our kitchen sink drain is blocked and only draining slowly. I have a bottle of One Shot acid - is it Ok to use on plastic pipes and what's the best procedure?

Instructions say remove as much water as possible first and then add water once you have put in 125ml acid - obviously I can get rid of the all the water in the trap but I was taught never to add water to acid.

Is it best to slowly add to the water in the trap and then wait and then flush some cold water from the tap?

Personally I've found the Mr Muscle foaming drain cleaner extremely good for situations like this as it coats all the gunk in the pipe. I've cleared a slow draining shower - took 3 goes but now the water just runs away rather than filling the tray to 3" deep.

To answer your question, we'd need to know the make of the cleaner - or its ingredients.

Your teaching only applies to adding water to concentrated acids where the mixing releases a lot of heat - notable conc. sulphuric acid. Conc. HCl is no problem mixing with water. Also applies to sodium hydroxide crystals.

It's basically 90% sulphuric acid - see

Just pondering whether this is best not used in plastic drainage pipes.

It's very strong sulphuric acid. As you say, you can drain the trap before adding the acid (don't forget to put it back together first!).

125 ml of acid should sit comfortably in the lower part of the trap, but when you add the water it will probably react violently, possibly causing a fountain of boiling water and acid to emerge like a jet from the plug-hole. Apart from then attacking anything it lands on, like the SS sink, work top, pots and pans, an inquisitive child who's crept up behind you unnoticed, it will also attack you if you happen to be in the way, which you may well be if you're still pouring the water.

If it were me, I'd try a less corrosive dra Sulfuric acid 91 % Reacts violently with water. Wash promptly if skin becomes contaminated.

This may be of interest

To be honest, it does not seem the best. Bleach is sufficient to take out the living scunge and to a degree attacks grease - the problem is it doesn't get to the upper parts of the pipe, which is where the foaming stuff comes in handy. I've only ever used acid on limescale.

I'm not sure if the OP means the U bend trap under the sink, it which case why not just remove it? When he says kitchen sink 'drain' could that be outside>

One Shot is usually added to water in a WC, technically the wrong way around, but you can't do anything else. As you say it will badly damage SS sinks, chrome wastes and anything else.

I use it quite often, but I'm ultra careful as you have suggested.

Probably less likely to affect plastic pipes than metal ones.

That rule is specifically for sulphuric acid. I've just looked, "One Shot" claims to be 94% sulphuric acid, if it really is that strong then, yes, you should add acid to water. However, I'm amazed that they're allowed to sell acid that strong, if it really is.

Follow the instructions would seem to be the best idea to me.

Why not just take the trap apart and clean it out?

No, it's the right way round, add concentrated acid to a large volume of water is the safe/correct way round.

Have you tried the obvious?

Sometimes correct depends on the purpose. I use concentrated caustic soda - Sodium hydroxide -- down in the U -bend and ad hot water.

It is explosive, but it clears the bloody drains all right!

You just need to not get skin or eyes in the way of the caustic geyser.

Permanent blindness is possible.

The blockage is further down the pipework and buried under the kitchen floor or in units.

One Shot comes in a plastic bottle :-)

It is that strong, trust me. Nothing else works quite like it.

That One Shot drain cleaner is in fact 91% conc sulphuric acid.

On a trip browsing around Lidl (an excuse for a cycle ride), I picked up one of those "that might be useful one day" purchases, which is a pipe cleaning kit you connect to a pressure washer outlet, like a smaller version of the ones Thames Water used up a blocked sewer.

About 2 weeks later, the kitchen sink blocked enough that the dishwasher pump-out backed up into the sink and then drained away slowly.

Took the U-trap off, but could instantly see the problem was the exit pipework was gundged up, with only about a 1/2" holw left down the middle for the water to flow away. Fetched the pipe cleaner from the garage, connected up the pressure washer, and it worked fantastically. Pushed the cleaning head right through until the pipe opened out into the 4" waste pipe from upstairs. The backwards-facing jets chisseled the grime off the pipe, leaving the small part I could see (and I assume the rest too) looking like nice new shiny plastic.

Cleaning head won't go around a U-trap, but it managed the other bends. I did have a little difficulty pulling it back out of the 4" pipe back into the 40mm branch, because a heatshrink sleave on the end was catching on an edge in the pipework, but it eventually released.