Soil pipe drop

[BigJoe79]

Hi All

New here so after a bit of guidance. We moved last year and after a short while noticed a pong in upstairs bathroom followed by toilet backing up every few weeks. I unblock it with a rothenburger plunger.

After unsealing the plinth I found that the waste is running perfectly horizontal and it’s been compounded by the fact that their are no support brackets so the section which terminates with a durgo valve dropped to create a dead leg for crap to acccumulate.

Nice previous owners had duct taped up durgo valve and sealed up plinth to hide it

So I am planning to lift the pan up but wanted to ask the following:

1. How much should I lift the pan to give more drop (the run to the vertical drop is approx 2m 24cm)

2. Will I need to lift the bath waste also slightly?

It’s a real pain as I am going to have to crack some tiles but I need to sort it.

Will probably put a grill somewhere in the boxing as I am aware the durgo needs ventilation to draw in vacuum.

Any help much appreciated.

Joe

 

[Doggit]

You need at least a 1 in 40 fall, and possibly a little more there. So you'd need to get the toilet raised by at least 2". You need to ask yourself, which is the lesser of the 2 evils, cracking the tiles, or working from outside, and readjusting the pipe exit. The box section won't be completely sealed, so air will easily get into the AIV, and being boxed in, you shouldn't get any of the smells that invariably escape from the valve when it operates. You haven't mentioned how the bath waste is connected, but it very likely goes to a boss outside the bathroom, so might need a little adjustment if you make the changes externally.

 

[BigJoe79]

Thanks for swift response.

Working from outside isn’t an option it’s an 80’s house so vertical is boxed in just inside outside wall.

To clarify the outside wall is where the bath taps are, so horizontal waste goes along behind bath and then drops.

In a round about way the bath shares the toilet waste so another whiff escape route when kicking up!!

I just checked and height of pan is 15” and they do some at 17” so for the sake of £100 would look a lot less Heath Robinson than a ply riser provided the outlet is 2” higher.

Joe

 

[Madrab]

You need to measure the floor to spigot centre height, most toilets are 180mm some are 190mm and some are 200mm, the height of the toilet itself won't necessarily dictate the height of the spigot centre.

 

[Doggit]

As there should be water in the bath trap, so you shouldn't be getting any wiffs from the there. And you may not be able to raise the waste pipe much as it might then hit the bath. If you can raise the toilet by adjusting the spigots as Mardrab suggests then you should be able to use a diamond blade on an an angle grinder to raise the pan, and then re-silicone it back in. But I have a nasty feeling that you're going to have to remove the bath to get this set up correctly, and may even have to raise that as well.

 

[Madrab]

To be honest you may need to crack open the bath panel/surround too, you need to see what if any fall there is on the soil pipe, that'll allow you to see exactly what's needed and whether and by how much you may need to raise the toilet.

 

[Nige F]

Can't see anything (other than the concealed cistern) down the boxing However I am guessing that the horizontal soil pipe has the WC going into a T -flowing behind the bath with the other end running level then a bend up and the AAV . So the WC is discharging straight @ the back of the T - not into a bend ( as it should be ) then the AAV could be on the top of the horizontal pipe. Modifying like this will allow the water to flow faster out the WC and may clear the horizontal path without any mods. Whatever happens you'll need to remove boxings etc. so do that and post the pictures

 

[Ian H]

If there is no fall on the toilet pipe the bath waste must join on the horizontal section of the stack, unless the bath is very high.

I think Nige's idea of the bend is a good one, the turds will be pushed towards the stack rather than going both ways in the current T.

 

[John D v2.0]

I guess someone moved the toilet position and thought they could get away without gravity.
Minimum fall allowed by building regs is 18mm/m but you'd want to minimise the number of bends especially elbows. You may be able to rejig the layout at the start of the run but as above you'll have to open things up unfortunately.
I'm guessing it is wrong because it wasn't easy to get right, frustratingly.
Our builders tried to lay a 2.5m soil pipe on the floor of our downstairs loo with two 90 degree elbow in because it was easier for them!. I told them don't bother, then I had to drill through a solid 9 inch wall and dig out parts of the oversite to do the job properly.

 

[BigJoe79]

Can't see anything (other than the concealed cistern) down the boxing However I am guessing that the horizontal soil pipe has the WC going into a T -flowing behind the bath with the other end running level then a bend up and the AAV . So the WC is discharging straight @ the back of the T - not into a bend ( as it should be ) then the AAV could be on the top of the horizontal pipe. Modifying like this will allow the water to flow faster out the WC and may clear the horizontal path without any mods. Whatever happens you'll need to remove boxings etc. so do that and post the pictures

Yes you have got it. That’s exactly the set up.

Thanks for everyone’s helpful hints looks like a bit of re-jigging required and once I have the boxing in opened up I’ll share what I find.

I suspect I will have to lift everything - with two kids putting half a roll of loo paper down it’s going to need all of that 2” drop!!!

Joe

 

[Hugh Jaleak]

If it's an 80's build then I bet the original pan has been replaced, and the new one being Horizontal Outlet, bodged in to fit the original outlet set for a P trap pan. Saw a classic on another site yesterday, HO pan replaced P trap, offset pan connector used upside down to make up the height difference between pan outlet and soil pipe, customer complaining their new toilet kept blocking....