What is minimum drop for waste pipe?

[TheMitchells]

Can I ask what is the minimum drop for drains?  We are looking to move our bathroom upstairs and the easiest option is to drop the waste from the new loo, down through the lounge corner into the cellar, across into the old waste pipe where it exits the house and runs into a drain outside. But it is a fair distance in the cellar, approcimately 4m then a 90o bend and another 8m.  What would be the minimum drop and whats the best way of measuring it?  Do I need to buy a laser level? 

[Gone West]

I work to 1:40 for foul water drain pipes and 1:100 for just water.

[PeterW]

As @PeterStarck says, 1:40 to 1:80 depending on the run for a WC

[TheMitchells]

Thank you - I guess I need to accurately work out the best drop we have.  Does having a 90obend make a difference?  The room will have a loo, bath tub/shower and sink so hopefully the water will help keep the waste pipe clean.

[PeterW]

Do you mean a 90 in the horizontal plane..? ideally I would use a long swept bend or two 45 degree bends.

[Ferdinand]

I'm assuming that Peter's 1:40 number is the one from the Building Regs (2.5cm per metre sounds about right).

 

To my mind it is equally important to make sure that it is downhill everywhere with no "puddle spots".

 

As to how to measure it - hadn't thought about that ! 

 

It could be a good excuse to get a laser level, but since soil pipe comes in 5m lengths and is quite rigid it may be easier than you think to measure from 2 or 3 points. I think I would measure every 2-3m using my long spirit level crewed to a straight batten.

 

I might even do it  by counting one brick (75mm) of height for each 3m, fixing a couple of nails, and laying the batten across one nail and measuring the vertical to the other, then adjusting, and putting my brackets *there*.

 

Having had some "ishoos" with slack drains, I might make it a bit steeper for luck.

 

Ferdinand

 

 

Edited August 7, 2016 by Ferdinand
Typo

[ProDave]

a 1 in 40 drop is 25mm drop in a 1 metre run.

 

To measure that, I have a standard 1 metre long level, and I tape a small bit of 2*1 timber to one end of the level, then set the pipe so the level reads level and you have a 1 in 40 fall. You won't get any droops or puddling at that fall.

 

You can go to 1 in 80 if you are short on fall. Then you have to be more particular that you can't get droops in the pipe run.
 

[PeterW]

It's more important to make sure it's even and no more than 1:40 - counterintuitive but if you make it steeper you lose the water and leave the solids behind ..! (Sorry to those eating their Sunday breakfast ...)

 

building regs quote 18mm per metre for stubs, unless it is tight on space where 9mm is acceptable as long as there is more than one WC on the stub branch - guess what I was reading last night ..!!

 

At 18mm, that's 1:55, 9mm is only 1:111 so you can see there is some discrepancy even in the regs themselves. 

 

[TheMitchells]

okay, I think I have all that.  I have borrowed a laser level so will try to measure the available drop tomorrow to see if it is doable.  I do hope so or we may have to give up on the bathroom upstairs idea.  We have been trying to trace where our drain goes and so far, no luck.  It does not go where we thought it went so now we havent a clue where our waste goes. That means we will not be able to take the waste stack outside at the front and connect it into teh drain as we dont know where the drain is at the front of the house!  Weird.

[curlewhouse]

Have you tried dowsing it to find the missing drain? Been discussed elsewhere, but all I can say is that it works for me every time. Just two bent rods from wire coat hangers will do. This guy is using the simple method that works for me. Works for my daughter too, but not my wife. No idea how it works, but it does! http://www.bing.com/videos/search?q=how+to+dowse+for+a+pipe&view=detail&mid=621C19A447668C1696B8621C19A447668C1696B8&FORM=VIRE

[Oz07]

12m X 12.5mm is 150mm fall

 

thats if if the full 12 is horizontal and at 1:80. Plenty of force if just dropped from 1st floor level. Plenty of clips in pipe to keep nice and straight if hung from joists

[Nickfromwales]

A long radius bend will give a near silent change of direction for the 'contents' of the pipe. 2 x 45's may create a bit more noise IMO. 

Have you thought about getting a camera survey done. A bit more concise than dowsing tbh, and if you'll be excavating then I'd want 'concrete' evidence before the shovel came out. Call me sceptical but I'm on the fence with this dowsing business .

Fwiw, as long as you have 5mm + per metre you'll be fine. Just getting BCO to be happy will be the grief but I've got of the hook before by being able to demonstrate the operation of the soil network, from flushed item ( big handful of bog roll ) to the manhole outside. Fitting a Y-branch directly after ( downstream ) of the swept bend will get you, ahem, brownie points   

[TheMitchells]

yes, I did consider using a camera for the drains.  Not sure how much they cost but will look into it.  The current thinking is that it will be far easier to leave the bathroom where it is and have two large bedrooms upstairs.  But that leaves us with a dark small middle room.  One way of improving the middle room (and adding a little wow factor into the resale value) is to remove the 18inch thick stone wall/pillar between the room and the kitchen which will give a larger single room kitchen diner. The issue is the thick rubble stone wall thats above the wall/pillar.  We will need some help on deciding whether that worth doing and if it is, how we go about doing it without the whole back wall of the house falling in!

 

This is the only shot I have of the pillar (taken before the previous owners moved their things out) - its the bit with the clock on it. The open doorway used to be a window and was made into a door sometime ago.  So there is some sort of lintel above it anyway.  where the coats are is only one brick thick and to the right of that is the wall between our house and next door but it does not look strong enough to take the weight of a large lintel/rsj. so I am thinking that we will need to build a brick pillar on the right of the coat store.  But how do we support the weight of the back upstairs wall, while putting in a lintel.  I think that will need an experienced builder and structural surveyor to get right.   More to think about.  Good job we are not in a hurry to do this job - it gives us time to change our minds! 

To clarify - the small kitchen is a single storey extension so that wall with the clock and coats is the main back wall fo the house and is very think rubble stones. 

 

In the meantime, I may get those coat hangers out and see if I can find the drains.  Got to be worth a try. 

 

Edited August 28, 2016 by TheMitchells

[Nickfromwales]

Pop the manhole up,and try a bit of old fashioned echo-location. Turn a sledge hammer upside down and with someone ( unlucky ) dangling their head in the manhole someone else goes around and gives the ground a good thump. Audible feedback at the manhole gives you at least some indication and it's free. 

[Nickfromwales]

Oh, and to avoid a pillar you may get away with a pair of concrete lintels, say 150x100x1200/1600 sat atop the wall to act as pads. 

I did this I'm my neighbours house as the steel needed to be where the original bit of wood sat which was the sliver of brickwork between the two alcoves ( 1 which was the right hand alcove in the dining room, and 1 which was the left hand alcove of the living room ) where divided. No wonder when my neighbour asked me to investigate it was prompted by his coving coming down by an inch at this junction !!

A pillar would have ruined the flush look of the wall as it traversed the new open plan liv / din room so I went at it that way. Still up lol. 

[TheMitchells]

Hmm - its certainly an area where we need help.  My father is having nightmares involving lots of house walls falling down!  And we are only just talking about it......

[Nickfromwales]

Situations only get out of hand if unsuitably managed. One example was a house in Swansea town centre where someone did a knock through. Only thing they didn't do was assess the integrity of the ground upon which they sat the acrows on. 

Wish I took a pic tbh, but it think I was put off by the fact that I really didn't fancy being in the builders boots. The centre section of the pine end had dropped by about 600mm with what seemed to be only the still intact part-rotated windows holding it in place. 

I did one on a 3-storey brick townhouse and my arse still wobbles when I think of what would have happened if that one 'dropped'. Lucky for me I put twice as many props in as was needed so I slept well for the one night it was unsupported. 

Caution, with a smidgen of fear is a healthy mix to ensure you follow procedure.....and then some. 

If you chose to go that way make sure you chose someone inventive and that they offer more than a simple "footing and pillar" option   

 

[Onoff]

Back to "slopes" and I'm now hoping my 2 deg slope on my 110mm soil pipe is OK! What's that as "1 in *" ?

 

1 in 28 if I'm not wrong so way more than the 5mm per metre above!

Edited August 29, 2016 by Onoff

[Oz07]

Don't talk in degrees it confuses the situation! How many MM of fall per metre? Like nick says you can get away with less. I was talking to some civils blokes and they reckon they go 6mm per m on the bigger stuff

[Onoff]

2 minutes ago, Oz07 said:

6mm per m on the bigger stuff

 

Is this ref the pipe size or what goes down it? 

[Barney12]

1 hour ago, Onoff said:

Back to "slopes" and I'm now hoping my 2 deg slope on my 110mm soil pipe is OK! What's that as "1 in *" ?

 

1 in 28 if I'm not wrong so way more than the 5mm per metre above!

 

2 degrees is 3.5% thus 1:29. 

[Nickfromwales]

43 minutes ago, Oz07 said:

Don't talk in degrees it confuses the situation! How many MM of fall per metre? Like nick says you can get away with less. I was talking to some civils blokes and they reckon they go 6mm per m on the bigger stuff

 

At that tolerance it's paramount that the pipe is supported VERY well to keep it absolutely flat along it's fall. Normal plastic soil clips have a sag of prob 5mm or more so be very careful when doing horizontal runs   In extreme cases where the wall isn't flat, plumb and straight ( such as a n old basement ) I'd even consider using Uni-strut to make brackets and hang the soil pipe in some metal 110mm pipe clips ( like these ). That would also allow you to adjust the height of clips to set the fall just by turning the clips into the threaded bar more / less. 

[jamiehamy]

On 8/7/2016 at 09:03, ProDave said:

a 1 in 40 drop is 25mm drop in a 1 metre run.

 

To measure that, I have a standard 1 metre long level, and I tape a small bit of 2*1 timber to one end of the level, then set the pipe so the level reads level and you have a 1 in 40 fall. You won't get any droops or puddling at that fall.

 

You can go to 1 in 80 if you are short on fall. Then you have to be more particular that you can't get droops in the pipe run.
 

I'll second that method - we used it last year and it works a treat.