Bathroom Drain Blocking

[SaxLady]

Hi, we've been in our house about 7 years, and for the whole time had problems with the bathroom drains getting blocked. We are going to be moving soon, and plan to rent the house out, so we really need to get the problem fixed. Over the years we've had several plumbers come through, none of which could definitively tell us what the problem is - but they would clear it, and it would be ok for a couple of months before blocking again. We had a plumber come through that put a camera down the outside drains, and we found that it was not roots or problems outside that was causing the blockages, so it has to be directly under the bathroom. Being an elevated house, we are able to get under the floor and look at the plumbing and take photos etc to try and get suggestions. The people who had the bathroom before us remodelled the area and plumbing, and took the bath out, and left a pipe that obviously used to lead to the bath. We blocked that end up, but that hasn't made any difference. If you check a couple of the photos we took at

, you can see that where all the plumbing from the sink and shower etc join together, it leads to a larger pipe that lifts a bit and goes straight before angling down and going outside. We are wondering if on the straight bit that is lifting, hairs and grime are catching, and drying out and in turn catching other bits of hair and grime until it blocks, and we get it cleared by getting a plumber in, or putting acid down to break it all up. Do you think that if we were to replace that section with a similar section (if there is such at thing) that doesn't lift, and perhaps angles downwards the whole time instead of just going straight that might solve the blocking problem? We are in Australia by the way. Thanks in advance for your suggestions.

[BigBird]

I'm afraid this isn't going to be a very helpful reply but I can't help but make a couple of observations. (I did plumb my own house but apart from that have very little experience to draw on).

Is that configuration anything like the norm in Australia? What I see is the mother of all traps. Do you have a trap on each utitlity the same as here in the UK aswell? If someone had shown me that design my guess would have been that it would be asking a lot too expect the soil to all move around that system cleanly. Surely if a trap like that were normal it would have a drain plug at the very least and some way of clearing it?

I'll be interested to see what answers come up because I'd have guessed that you would be looking at re-arranging that plumbing to remove or at least reduce the extent of that trap.

You've had plumbers looking at it so obviously it can't be a simple as that. Like I said just amateur observations.

[Dave Liquorice]

Does seems rather odd by UK standards where individual traps is the norm. And where does the vertical large pipe go, to the toilet? In the second picture after the big trap (large U shaped bit of pipe) the diameter appears to significantly reduce from (guessed) 110mm of the vertical to 50mm for the outflow. This might be an camera illusion but the first picture also looks like that. This can't be good.

Certainly the flow from a bath or basin isn't really going to be fast enough to carry much over that size of trap. I'd even be suspicious about the flow from a loo, especially a modern low volume flush type, being able to clear it as well.

Assuming that the individual sinks, baths etc have their own traps I'd certainly look at removing that big central one but that might be against OZ regulations.

[Grunff]

This is exactly what I was about to post. Surely it can't be normal practice to put in a trap like that in welded pipe? It must need cleaning out on a regular basis.

[Hugo Nebula]

On Sat, 17 Jul 2004 06:22:18 +0100, a particular chimpanzee named "BigBird" randomly hit the keyboard and produced:

It also looks to me as though the main stack is 100mm diameter feeds into a smaller branch after the (unnecessary?) U-bend.

As I've posted before, never underestimate the laziness of plumbers. The whole thing looks like an awful mess, and one suspects that the reason that the U-bend was introduced is to give enough room to connect all the other branches into the stack. I've seen many similar installations with the excuse that "it's just sink/washing machine water, it'll never block".

[SaxLady]

Hi all, thanks for your replies - I asked this question elsewhere as well, and had very similar responses. Just to clarify then, if we were redesigning the whole system in that section, is this what you would suggest - (sorry I don't have proper plumbing technology!!) Get rid of the the main junction where it all feeds together and replace with ?? a single large pipe that has individual feeds into it from sink, shower and floor drain, sloping down at an angle between 1/4-1/8" per foot (apparantley that would give sufficient sloping for a slower flow as suggested elsewhere- not that I've measured the area to see if this is even viable, but we'll assume it is), therefore removing the need for the U-bend as well (which I assume when you've mentioned it is the section that rises and goes straight after the main junction before going outside?) I would imagine that both the shower and the sink would need individual water traps in this case, where would you put them? - just before they feed to the main one, or further up near the initial inlet? Or have I got it all totally wrong? Thanks

[SaxLady]

And just in addition as well - would the main pipe need it's own trap before it goes out to prevent possible sewerage backflow?

[Terry]

Just to add, also as an amateur, Canadian, plumber had no significant problems with our self installed systems for the last 44 years; firstly to a septic field at back of the property and then, some years later, we had to turn it round and run it in opposite direction to the municipal sewer in the street! Our typical plumbing is 1.5 and 1.25 inch drains into a 3 inch main drain with venting pipes to the roof 'stack' for each source, especially if it is more than (IIRC) six feet from the stack vent. So for example our kitchen sink is some 20 feet away but has it's own vent up to the common roof vent. Each source (kitchen sink, bath tub, vanity sink etc.), has it's own trap, often with a plug in bottom that can be taken out for cleaning. We don't have (the lowest level of our plumbing is at least 8 feet above the top of the nearest sewer manhole) but in many installation a 'back flap' valve is installed in the main 3 inch or 4 inch outflow to the municipal sewer. AIUI it is 'required' by some jurisdictions to prevent sewage back ups. I have no idea how well or badly they work. Again as a do it yourselfer plumber my suggestion would be to study that assembly and redesign it raising it up sufficiently by playing around with the various PVC plumbing bits available to not have that outgoing 'U' bend or trap on the bottom. With 'glued/cemented' piping you may not be able to reuse very much of the existing assembly. Before starting may be good idea to have extra 'bits' including some 45s. to 'angle' the existing individual runs into the main stack? Return leftovers when job is finished; alway keeping that downward slope in mind. I realize that gravity in Australia works 'upside down' and water in the bathtub swirls the other way; but after that it's downhill all the way! Sorry cobber! Couldn't resist. Terry Canuck!

[Pete C]

Hi,

Where do the pipes come in from?

cheers, Pete.