Installing sewage treatment plant / drainage field before house construction?

[flanagaj]

I've probably answered my own question here, but I am assuming that so long as you have your FFL datum point for the new dwelling, then installing your sewage treatment plant / drainage field is done simply by deducing the proposed location of the treatment plant, and the associated run length of the pipe to determine the corresponding invert level and associated fall.   We are hopefully (if planning allows) putting a static caravan on site and will need the sewage treatment / drainage field to be in place before development starts, and I am just trying to deduce the best way of getting it right so that it works for both the new house and the static caravan.

The only potential issue, is that the caravan is going to be sited on the opposite side of the tank and this will mean an interesting pipe setup, as it will have to at some point perform a 180 degree change in direction so that it can feed into the inlet side of the tank.

Not sure if this is a problem, or whether I need to consider trying to move the tank.

[joe90]

The answer is YES. and a temp connection using two 90’bends (or better still four 45’ bends ) will get you back to the tank, it’s only temporary.

[Kelvin]

Is there any danger of damage during construction? 

[saveasteading]

Its a good idea , saving money on hiring and disposal, and priming the tank for real action.

 

as @joe90says, it is temporary and so the bco will not be interested in the pipes until the final run goes in. If it blocks then you can clear it.

But the digester and soakaways have to be right and inspected.

 

But beware the levels. Joining the dots is fine as long as all the falls stay within the design parameters.

But things go wrong. Spirit or laser levels can be out of adjustment. Groundworkers , if you are using them, don't necessarily understand geometry or how laser levels work.

You may encounter obstructions and have to revise the design.

 

On our steading project I did the design and the hands on laying. When we found obstructions (big boulders, other pipes) we could make informed decisions as we went. These always mean going steeper for a bit, although bigger pipes was an option. the digester ended up 100mm lower than the original design. as it went in last it didn't matter, but the hole was getting uncomfortably deep.

You don't want to end up lower than the tank intake, or to have a flat last run to make it fit.

 

[Russell griffiths]

Set it up correctly for the house, the static doesn’t matter as it will be raised up on stands or blocks, you can also have a fair bit of pipe above ground for the static to get a good fall, install a rodding point at the static end and jobs a gooden. 
 

word of warning 

when connecting to the static make sure you strap the pipe up securely, I know a chap who used his toilet for months without knowing the pipe had come of, poo mountain under the caravan. 

[flanagaj]

1 hour ago, Russell griffiths said:

I know a chap who used his toilet for months without knowing the pipe had come of, poo mountain under the caravan. 

 

haha. Funny, but not pleasant.
 

1 hour ago, saveasteading said:

Its a good idea , saving money on hiring and disposal, and priming the tank for real action.

 

as @joe90says, it is temporary and so the bco will not be interested in the pipes until the final run goes in. If it blocks then you can clear it.

But the digester and soakaways have to be right and inspected.

 

But beware the levels. Joining the dots is fine as long as all the falls stay within the design parameters.

But things go wrong. Spirit or laser levels can be out of adjustment. Groundworkers , if you are using them, don't necessarily understand geometry or how laser levels work.

You may encounter obstructions and have to revise the design.

 

On our steading project I did the design and the hands on laying. When we found obstructions (big boulders, other pipes) we could make informed decisions as we went. These always mean going steeper for a bit, although bigger pipes was an option. the digester ended up 100mm lower than the original design. as it went in last it didn't matter, but the hole was getting uncomfortably deep.

You don't want to end up lower than the tank intake, or to have a flat last run to make it fit.

 

I am going to be doing the installation myself for this very reason.  

[saveasteading]

35 minutes ago, flanagaj said:

I am going to be doing the installation myself

The best thing I learnt in preparing for it was to use a 'prepared' spirit level, jacked up at one end with spacers blocks and sticky tapes.. that made it so easy compared with jumping in and out of the trench to use a hi-tech machine. or buying a fancy laser.

I'm sure that the errors of 1/2mm every time added up, but you can always do a proper check occasionally.

[joe90]

1 hour ago, saveasteading said:

The best thing I learnt in preparing for it was to use a 'prepared' spirit level, jacked up at one end with spacers blocks and sticky tapes..

I did exactly this, long spirit level with block taped to  one end to create the fall, no high tech to go wrong .

[Canski]

13 hours ago, joe90 said:

I did exactly this, long spirit level with block taped to  one end to create the fall, no high tech to go wrong .

As long as the level is used the right way round. 😀

[saveasteading]

13 hours ago, joe90 said:

I did exactly this,

It may have been you I got this from. This makes you a guru.

 

Having had groundworkers make huge mistakes with lasers I added this to my other lotech methods.   Battens bashed into  footings showing pour level. Nails in sides of trenches ditto. Golf balls to show falls on slabs and check drain runs. All highly recommended.

[joe90]

12 minutes ago, saveasteading said:

It may have been you I got this from. This makes you a guru.

Great minds think alike (I am a Luddite )