Drain keeps clogging

[szeik]

Hi,

I recently posted about water backing into our tub on the first floor where the tub, kitchen sink and dishwasher all share a common drain. After having a plumber out to snake it it started happening again today so I snaked it myself and this time I was able to unclog it myself. I learned a couple of tricks watching that plumber!

But the big problem is that it keeps reclogging so we must only be opening a small passage each time we snake it. A guy I know looked at our plumbing downstairs and pointed to a section that is older pipes and said if I replace this one section it will cure the problems. He thinks the insides of that pipe have mineral scale built up and that we are only clearing a small hole each time we snake it. There is a lot of plastic pvc that was installed when we had our kitchen and bath renovated but there is this one section that is the old stuff.

What do the plumbing experts here think about this?

Thanks, Steve

[roger61611]

Not an expert so much but if the old pipes are ferrous then heaven knows how much water is able to get through, they can really get filled with stuff, to the point of being useless. My experience applies more to the 1" supply (galvanized) and the 1.5" or 2" ferrous drain pipes, I don't know if cast iron 4" stacks ever get rusty enough to stpo up, that would be quite a thing to gaze into.

Personally I would rip out everything involved and do plastic, it's relatively cheap compared to the ongoing hassle.

Also make sure you're bored out, out to the sewer, do you have problem with roots, etc.

[Joseph Meehan]

...

....

There are other possibilities. The design horizontal runs at the wrong slope or wrong size pipes; condition of the pipes, a more serious clog further down, maybe roots outside. All kinds of possible issues.

[Dan Espen]

Here, feast your eyes on this, a 4 inch pipe about 40 years old:

[DanG]

I seriously doubt that the cast iron lines have anything to do with your problem unless they are not set to adequate flow grade. Cast iron can grow nodules on the inside of the pipe that snag scum and solids, but I have never seen any grown shut to the point of slowing water.

I suspect your problem lies elsewhere. If the original piping is fairly easy and it would make you feel better, go ahead and replace it. I just don't think it will be the end of your troubles.

(top posted for your convenience) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Keep the whole world singing . . . . DanG (remove the sevens) [e-mail]

[Des Perado]

[Stormin Mormon]

Larger tip on the snake? Cutting knife instead of spring?

[Stormin Mormon]

Dificult to snake that, eh?

[The Masked Marvel]

Cast iron shouldn't be problamatic (as DanG says), nor should copper, ABS or PVC, but galvanized steel might, due to corrosion, causing clogging. Lack of proper pitch is another possibility. The fact it keeps reclogging inplies something's wrong or that it's not being fully cleared. You should be able to estimate th edisitance to the problem by how much snake is req'd to reach the obstruction. If this corresponds the the older section you may have found the culprit.

[CL (dnoyeB) Gilbert]

In my sink that clogged about once every 2 months, the pipe went uphill a bit. this meant a lot of water was always in the pipe. we had a double sink. you could see the effect when you ran the garbage grinder or dishwasher and the water would start to push of the other drain till the rate was reduced a bit.

[ds549]

i had a kitchen sink that kept reclogging after a cleaning out. i went on the roof and snaked out the vent. that fixed it. lucas