Blocked sink waste pipe

[sagalout1954]

Perhaps if I start by saying it is NOT the U bend that's blocked - definitely.

Our bathroom sink has virtually blocked a few times over the past couple of years. Water drains slower and slower until it's all but blocked completely.

Usually 'fix' it by using a DiY thing like coiled spring stuff on a roll (inside a housing with a handle to make it 'twist' while it's being fed through), we feed it through the pipe by unscrewing a connection under the sink and shove it down through that, coaxing it through 2 'elbow' joints then as far as we can get it to go. Not the easiest process in the world. Followed up by some shop bought 'sink and drain unblocker' liquid overnight. Usually does the trick for a while anyway.

This time it seems worse so decided to investigate further, clearly our DiY methods have only been a temporary 'fix' each time. Waste pipe is boxed/tiled in so once box top is off access is limited to 'viewing' (more or less - can't reach down properly to pipework and no room to manouvre even if we had longer arms).

The sink waste runs the length of the bathroom, several feet in a straight line directly into the downwards soil pipe, the shower has a separate waste pipe. No access at all to the soil or latter part of the sink waste pipe, the shower stall is in the way. Definitely no other pipework connected to it, on it's own straight into the soil. Toilet has never blocked, shower waste OK too.

Determined that the sink waste pipe was STUPIDLY running in a slight UPWARDS direction towards the soil pipe!!!*** No wonder it keeps blocking. Anyway, have managed to do enough remedial adjustments so that it runs in a downwards direction from sink to soil.

Then gave it another 'rod' out as best we could, but judging by how much of our spring stuff being fed into the waste pipe, we can't get it to go the whole length right to the soil pipe. Put down some 'unblocker' liquid and this morning.............between little and no change.

Blooming thing hasn't improved despite having dismantled half the bathroom.

Now what - resort to a plumber?? What would they do to unblock the pipe? Any suggestions?

Sorry for epic posting, am trying to give clear picture first time around.

 

[ChrisR]

WHat diameter is the pipe. From a Basin trap it's usually 32mm ( inch and a quarter) but it's supposed to be bigger if it's more than 1.2metres.
But it should flow reliably if it's all downhill.
If your snake's a bit short it's opbviously possible that you've pushed a blockage enough to make a wall, so get hold of a longer snake!

The ultimate drain clearing liquid is sulphiric acid. It 's what's in some of the more serious drain cleaners you'd get from a plumbers merchant. It'll say on the lable. It dissolves almost anything, like hair, arms legs etc, which some of the others don't, but it's damrned nasty so be careful with it. Very careful. Use a funnel or cut off top of an old bottle. Pour some in, leave a few minutes, repeat, repeat, or it'll all run away.

If you still have a problem, it could be you're getting an air pocket stuck in the pipe - especially if it sags or goes up a bit. Then a "Vented" or "anti vac" trap can help.

 

[sagalout1954]

Thanks ChrisR for advice. Decided to resort to sulphuric acid from plumbers merchant as an overnight dose of something less strong shifted it a bit so a full sink of water would empty in 4 minutes instead of the previous 11 1/2!

Have been very, very careful with the sulph acid, following instructions. 250ml carefully poured down using a funnel. After 10 mins supposed to slowly add 500ml of cold water, got 300ml in when it started to slowly rise back up into the sink by about 3/4 inch) giving a gentle bubble 'belch' like a volcano up through the plughole (doesn't splatter at all).

Been like this for about 1 hour. Given that in total liquid we've poured down of acid plus added water was only 550ml, we're not sure if this bit of bubbling excess is caught only in the U bend?

The whole pipe is approx 2 1/2 mtrs and the blockage is approx 2mtrs along it. Think we determined this with our 'snake', which seemed to travel freely that far before it refused to go further.

We are supposed to 'flush' the acid out with more water, but reluctant to put more into the sink in case the whole lot won't move. Definitely had some flow (though slow) this morning.

 

[hi1]

Leave it for a while, try and introduce some more of the acid, its thicker than the water so should sink to the bottom of the system where its blocked and dissolve the blockage, don't add water yet as that will just dilute the acid and reduce its effectiveness. The bubbles are the gases being given off from the dissolved stuff, hair usually. If its stopped bubbling its because you've diluted it to early.

 

[sagalout1954]

Wow, that's us done with the dangerous substances. This stuff has been backed up into the sink all night doing it's little volcano bubble every now and again.

Finally slipped back down the plughole to about an inch and half between 4.30 and 7 am (the times when I got up to check it, didn't get a lot of sleep!!)

Has stopped bubbling but hasn't drained away either.........time to call a plumber. Will be sure to make it clear sulphuric acid has been used and still in there.

Bit odd though, as I've said, this pipe is about 2 1/2 mtrs long, was blocked about 2 mtrs along (think). We've probably poured down maybe 600ml of liquid (inc water), surely the whole pipe from blockage to sink can't be full of this liquid.

Oh well, time for the cavalry. Thanks anyway, was worth a try.

 

[hi1]

There will be fluid down the plug hole it forms part of the trap to keep foul gases entering the room. The fact that the level has dropped means the obstruction or some part of it has been removed, the lack of bubbling either indicates the obstruction has dissolved or the acid part has been used up in the subsequent reaction. Pour some more acid down the hole, let it do its work then try running water. I've never been let down by this product, one shot, it managed to remove the blockage of 3 toilets all connected in a student let, need i say more.

 

[sagalout1954]

You're right Hi1, what liquid that we could see WAS only in the 'U'/trap. Plumber promptly stuck a bucket under and undid it. The resulting liquid went all over his hands where he had a couple of cuts! I learnt some ripe swear words as I led him to an alternative water source to wash the acid off.

I WARNED HIM MORE THAN ONCE WHAT IT WAS AND EVEN SHOWED HIM THE BOTTLE BEFORE HE STARTED ON IT. His choice to burn his skin.........nit.

When reassembled, still blocked, but he made easy work of it. Was happy with the 'lifting' job we'd done on saggy middle, happy with shortening 'down' part of sink pipe so instead of water waste flow trying to rise UP to soil pipe it would flow DOWN once blockage removed.

Sawed off pipe at sink end, complication of inaccessibility of other end where the waste pipe met the soil pipe was no problem after all, he simply pulled it and it came out!!! Pity we didn't realise it would be that easy or we'd have done it ourselves.

Sawed the pipe in half so it could be removed altogether, FULL of great clods of very hard, white material. Looked like toothpaste, soap, Jif and limescale. Bad initial 'uphill' plumbing to blame, encouraging the 'saggy' effect as gunk settled there, building up over the years, knocked/poked it all out with rods, nice clean pipes left.

Put back in place with join at sink end, shoved back into soil pipe at other end, with pressure joint in middle "in the unlikely event this ever happens again". Not a single drop of water spilt or dripping. JOB DONE.

Took 1 1/2 hrs, cost £114 inc VAT and parts. Bit worried about plumber, I had the windows open but by the time he left he felt very hot and had a bad headache. I gave him some paracetamol but don't feel responsibile - he was warned. No protective clothing/gear whatsoever.