Making a start with drainage

[charlie-ia]

we cleared the grass away and started removing the soil around our very wet walls. imagine our joy when we discover one side of the house has a flagged path and a concrete gutter, which is in good repair. the gutter is about a foot wide curved shallow channel.

How do i accurately measure how the floor levels compare?

every where i measure gives a different result because every thing is so uneven. also im trying to guess where the top of the internal wall matches on the outside, so i dont have a fixed reference.

what if the gutter is a bit (2"-6"?)above the internal floor level? will we have to remove it? i cant decide if it is protecting the wall by channeling water away, or causing harm because it's the dreaded "concrete right up against the walls of the house" .

the concrete gutter drains away into a cobbled "gully" into which the kitchen sink also drains.Really beautiful at the moment (red sandstone), but probably not so nice if its full of dishwater scum.
if i divert the sink, will the cobbles be ok for draining rainwater away, or should we point it or something? will the cobbles allow water to seep into the foundations? they clearly breathe, you could see them steaming in the sunshine.

we have yet to discover where the water goes to!

We were also able to remove all the lino and polystyrene indoors. standing water on all floors.
the kitchen is also beautiful sandstone flags. just like we imagined in the best case!
opening the doors and windows and a bit of sun have made a real difference already. ive read that on here so many times, but untill i saw it with my own eyes... the smell cleared up when i got rid of the dead crow too!

 

[Gervase]

The best way to check levels when you can't see both surfaces is with a water level - a long piece of tube open at both ends that you fill with water and use with an assistant to find the levels. It's very accurate and can work round corners, up and down stairs and through open windows.
As for the gutter height - ideally it should be below the floor level. But why not give the walls a few weeks to dry out and see if just removing the soil has made a difference.
My gut feeling, however, is that the concrete ought to go! Replace it with a perforated land drain pipe at least six inches below floor level at the bottom of a trench filled with shingle. It'll look nicer than concrete as well.

 

[alice]

I was going to suggest a water level, although I didn't know the official name. My name was Long Length of Clear Aquarium Tubing With Water In It. Your name is much more concise!

alice

 

[Penners]

The best way to check levels when you can't see both surfaces is with a water level.

Just make sure that you don't fill it with water from a water-skiing lake, as this will have a slope on it.

 

[arl]

filling it with one of those lurid kids soft drinks makes it much easier to see (just dont use a fizzy one - only last month my other half was frothing at the mouth trying to syphon cherryade )

 

[charlie-ia]

Well thanks for that, looks like a nifty thing.
could you just clarify how you use it- put both ends together, mark the two levels, nip round to where you want the measurement with one end and read it the levels again?
does an inch change represent an inch in height? how do you calibrate it if not?

will the cobbles be alright as a drain without doing anything to them?

 

[chuckey]

water levels are simple in theory,but I have had problems with them. 1, air bubbles, the pipe must be purged of all air or it will take forever to settle to the correct level. 2, Proper levels have a "pot" at each end to act as a fluid resevoir, a crude way would be to have a pipe upstand of say 2' at each end. Otherwise moving the pipe around, results in loosing fluid and then getting air bubbles. c, Some form of support for each end, weighted with a brick or staked into the ground.
Or establish your reference from the bottom of the glass in a window frame, cos' you can see from the inside.
Or better still, invest £20 on a laser level and make your own target, a bit of card or hard board nailed on to a piece of heavy timber so it stands upright.
Frank

 

[Gervase]

An inch difference in the pipe equals an inch in real life. Those things are accurate to around 1mm in 100 metres, which is better than most lasers.
The better ones have a little bleed valve on each end so you can completely fill the tube with water, put it where you need it and roughly guestimate the levels, then fine-tune with the bleed valves.
As for the cobbles, how far from the wall are they, and what are they bedded in?

 

[charlie-ia]

A cobble pathruns the full lenght of the house and maybe more.
it runs parallel to the concrete drain at the top end of the house, with beautiful large kerbstones.
then theres a flagged area by the door with a narrow channel (aprox 3" wide concrete) touching the doorstep. there the concrete ends and drains into the cobbled channel that runs right along the lower end of the wall and is about 2ft wide, still with the cobble path and kerbstones.
at the moment they just look like theyre just laid into the soil, no sign of any type of pointing (if this is the correct term). theyre all pretty firm, and we havent looked underneath.

i wondered if the concrete channel had been put in due to trouble with the cobbles. the cobble drain may still exist under it.

 

[Penners]

Those things are accurate to around 1mm in 100 metres

Interesting. I'm very surprised that there is any measurable inaccuracy at all - even one as small as that. Surely the principles of physics make any inaccuracy impossible?

Or are we into the realms of things like surface tension?

 

[MdB]

Those things are accurate to around 1mm in 100 metres

Interesting. I'm very surprised that there is any measurable inaccuracy at all - even one as small as that. Surely the principles of physics make any inaccuracy impossible?

Or are we into the realms of things like surface tension?

Differential air pressure, the definition of level (perpendicular to gravity / perpendicular to the centre of the earth), Coriolis effect, tidel forces and I am sure many other minor effects will move the level away from being perfectly true though all of these will be tiny and I am sure a lot less than 1mm over 100m though I've not done the sums.

 

[Penners]

Hmmm - not sure I can see how the Coriolis effect would be a factor, since this is a perceptual effect rather than a physical one.

Perpendicular to the centre of the earth? Surely this would add to the accuracy, rather than detracting from it.

Atmospheric pressure? Yes, perhaps. Although over the space of a kilometre, I'd be surprised if it would have as much as a 1mm effect.

 

[CHRIS]

Penners

If you are interested I have done some gravity surveys for the USGS in the USA

Here is the type of thing that is done

http://66.225.140.1/minsci/finding/gravity.htm

http://pubs.usgs.gov/imap/i2687/.

But I am sure that a water level is fine for this matter!!!

Here a few types that you could use, but as chuckey mentions the bubbles are a pain so I just dangled mine (the water level !) out of a 10 story building to get them out.

http://www.yorksurvey.co.uk/products/prods2/levels/waterl.htm

 

[MdB]

Hmmm - not sure I can see how the Coriolis effect would be a factor, since this is a perceptual effect rather than a physical one.

The pipe is being rotated (by the earth) so there will be a Coriolis force on the water. The effect will be very small but it will be there and will depend on the length / position of the pipe I think. I'm open to corrections on this as Coriolis forces are a bit brain warping to think about. They were used in inertial nav system I worked on to work out the heading whilst stationary but I could never understand the process properly.

Perpendicular to the centre of the earth? Surely this would add to the accuracy, rather than detracting from it.

The force of gravity at most places on the surface of the earth does not pass through the centre of the earth due to a number of effects, the main one being that the earth is not a sphere. This will again make a tiny error in the water levels if your definition of flat is perpendicular to the centre of the earth (not that this is a good idea). If your definition of flat is perpendicular to the local gravity (a lot better idea) then there will of course be no error.

Atmospheric pressure? Yes, perhaps. Although over the space of a kilometre, I'd be surprised if it would have as much as a 1mm effect.

I would be surprised if it was 0.1mm but it is another effect that will make the result something other than 100% correct.

Not that any of this matters. The combination of all the above errors is going to be a lot less than 1mm over a considerable distance. Getting the bubbles out of the pipe will be the biggest issue on accuracy.

 

[CHRIS]

MdB

You would be suprised but if you are measuring from inside a tunnel using an EDM http://en.wikipedia.org/wiki/Total_station and the air presures are diffrent (they are often are) at each end of the line you can get about +/- 3mm over about 150m. It is good practise in tunnel surveying to take air presure readings at both ends of the line when transfering lines in and out of the tunnel.

If the slope of the line is steep (air shaft into the underground springs to mind) this is often done at various times of the day and an average is calculated.

We use inertail systems on ROVs on subsea construction vessels, is this you game?

 

[MdB]

I would assume that mines are little different due to forced air ventilation or are there other effects in play? I did once wonder if you could generate electricity off the channel tunnel due differences in air pressure between the UK and France though. Would this work?

My INS work was for aircraft where knowing where you are going and knowing where you are pointing where rather important questions. Side slip is a wonderous thing when navigating.

(oh dear is this another thread that has gone totally off topic....)

 

[charlie-ia]

(I agree! what about my lovely cobbles?)

 

[Nemesis]

Can you post some pics?

 

[CHRIS]

We have a correction that is applied to mesurements when decending or climbing through forced air enviroments such as mines or deep tunnels. Basically it is done by looking at 2 diffrent coloured lights and compairing the bend of the beams through the change in atmosphere and presure.

Have a look at PARA 4 in this PDf,

http://www.geometh.ethz.ch/downloads/eisenstadt98.pdf

they used the channel tunnel as a model for the surveying as it is one of the best ever miscloses in any construction projects

(sorry about hijack)

 

[Penners]

This is fascinating stuff, but all getting way beyond my level of comprehension.

However, it seems that for Charlie-ia's requirements, a water level (with bubbles avoided) is going to be error-free, to all intents and purposes.

For myself, I just want to know where on earth gravity is weakest, so that I know where to put my bathroom scales.