60 Year Old Water Main

[PeterW]

Grey water from the shower and basin to a soakaway ..??? 

[ProDave]

11 minutes ago, PeterW said:

Grey water from the shower and basin to a soakaway ..??? 

Hope it's ONLY the grey water he is taling about.

Seriously you don't do that. Update the cess pit to a treatment plant and a soakaway.

[Onoff]

5 minutes ago, PeterW said:

Grey water from the shower and basin to a soakaway ..??? 

I take it that's a no-no then?

At the mo the shower/basin/bath wastes just go to a giant, brick built, arched roof cess pool (of indeterminate condition) along with everything else i.e. the rain water and WC stuff that side of the house. The other side of the house is apparently another soakaway (not sure where) that takes rainwater from that side.

[Onoff]

2 minutes ago, ProDave said:

Hope it's ONLY the grey water he is taling about.

Seriously you don't do that. Update the cess pit to a treatment plant and a soakaway.

Well I had just intended the grey water into the soakaway....but that's not allowed?

[PeterW]

Nope ! 

Can you split out the rainwater into a soakaway ..? That will just fill and dilute the cesspit and you'll end up having it emptied more often. 

Sounds like the treatment plant is next on the list ..! Good job you know someone with a mini digger ..! 

[Onoff]

WTF is a treatment plant? Seriously, something new to learn about! One of those "seen the words but ignored until now".

Yep, the rainwater could go to the soakaway easy enough and leave the grey water and WC wastes going to the cess pit. 

Blank canvas pretty much outside.

[Jeremy Harris]

13 hours ago, Onoff said:

WTF is a treatment plant? Seriously, something new to learn about! One of those "seen the words but ignored until now".

Yep, the rainwater could go to the soakaway easy enough and leave the grey water and WC wastes going to the cess pit. 

Blank canvas pretty much outside.

If you're off mains foul drainage, then there are three options, and the law was being changed to pretty much force everyone towards the most favourable one, in environmental terms, but I think that the EA (SEPA in Scotland, DOE in NI) just have too much work on to even look at enforcing the EU legislation on this.

The least favoured option is a cess pit or tank.  This has no means of treatment, will be highly septic (it's anaerobic) and needs frequent emptying, as it is just a sealed tank with no drains from it.  You can now only fit one to a new build if it is for short term use or under special circumstances - BC try hard to dissuade their use.

The next option is a septic tank.  This is also septic (anaerobic, as its name suggests), but it makes the effluent it discharges safe by tertiary treatment by aerobic soil bacteria around the land drainage pipes that take the liquid effluent away.  Septic tanks have a limited useful life, as after a few years biological films build up around the land drains and so stop oxygen reaching the soil around them.  They then become septic and present a hazard because there is reduced aerobic tertiary treatment.  After around 10 to 15 years the general consensus is that septic tank land drains won't be working as tertiary treatment and pathogens will be being discharged to the leach field, which is why the preferred option, treatment plants, have been invented.

The preferred option is a package treatment plant, approved to the EU standard.  This is not a septic tank, it operates under aerobic conditions, and so is very effective at removing pathogens and massively reducing the BOD (biological oxygen demand) of the discharged effluent.  Treatment plants look a bit like septic tanks, except that they have a means to oxygenate the whole content (usually including the solids) by means of a mechanical system, an air pump, or some form of air permeable media and a ventilation system.  The effluent from such a treatment plant is safe to discharge to a large soakaway, constantly running water course, a soakaway mound, or conventional land drains.  No tertiary treatment is required by the drainage system, as the effluent is not septic and does not have a high BOD.

[ProDave]

Pictures are good. Here's my treatment plant being lowered into it's hole.

This is one of the designs that works with an air blower, and much like a lot of the other air blower plants gives just about the cleanest effluent possible. It costs under £2000

I would personally avoid the designs that use mechanical rotating parts, as I personally would not wish to be the one reparing them when dirty mechanical bits fail.

Are you SURE you have a cess pit? if you do you will be emptying it very frequently. Are you sure it's not an older type concrete built septic tank?

[Jeremy Harris]

1 hour ago, ProDave said:

I would personally avoid the designs that use mechanical rotating parts, as I personally would not wish to be the one reparing them when dirty mechanical bits fail.

Are you SURE you have a cess pit? if you do you will be emptying it very frequently. Are you sure it's not an older type concrete built septic tank?

Me too - having looked at some of the mechanical ones my first thought was that they would be a maintenance nightmare, which is why we ended up with a unit very like your's Dave.

I doubt that Onoff has a cess pit, I too suspect that it's an old septic tank with land drains going somewhere.  I've seen some old ones without land drains, where a few bricks have just been left out to allow the thing to drain, not nice putting raw sewage into your garden.

[Onoff]

I know ROUGHLY where it is as mad as that sounds. In/under a very overgrown area of the garden which I've yet to get to. No trees as such but a good few bushes. We had tbh the very basic survey done when we bought the place and that didn't pick anything up I'm sure. Speaking to the previous owner about the water main he reckons the same guys dug the "cess pool" so whatever's there is circa 60 years old. He remembers it being a massive hole dug by hand, brick built and with a brick built arched roof then covered in dirt. The oddity is that there's no foul smell in the area, no apparent liquid discharge either. I am wondering if either the "bottom" is cracked or there isn't one. It'll be a case of gingerly scraping the top soil off at some time to find what area it covers. As for emptying it - never had to. Just another mystery in the house that Jack built! 

[Jeremy Harris]

It was fairly common in years gone by to just dig a hole and build a brick-lined chamber, with a few bricks missing around the top to allow the liquid effluent to seep into the ground.  They are far from being hygienic, as there was no treatment at all with a system like this, and nothing to stop pathogens from breeding and infecting the soil around the tank, or even penetrating aquifers and watercourses.  I helped dig one out many years ago, and all the soil around the thing was deep black and exceedingly smelly.  We dug out all the soil for around three or feet away from where the old brick lined tank had been, and spread it over a field, where it will have gradually been made safe by normal soil bacteria.  Not a pleasant job, it has to be said!  We replaced it with a Klargester "onion" septic tank, with perforated pipe land drains in pea shingle filled trenches running away across the adjacent field.  That's still apparently working, but it's 20 odd years old, so my guess is that it's really just draining raw and untreated effluent into the field by now.

A proper septic tank will be sealed and will have a drain (or drains) coming from near the top running out to relatively shallow land drains.  Nowadays these land drains will be perforated pipe, but older ones either use unjointed clay pipe sections, with gaps between the joints, or field-type land drains with just a trench filled with stone or hardcore.  All these forms of land drain stop working after a few years, in terms of treating the effluent, but there won't be an outward sign of this, the effluent will still drain away it will just remain septic in the deep soil, where there's not enough oxygen to allow aerobic bacteria to treat it and make it safe.

[Onoff]

9 hours ago, JSHarris said:

It was fairly common in years gone by to just dig a hole and build a brick-lined chamber, with a few bricks missing around the top to allow the liquid effluent to seep into the ground.  They are far from being hygienic, as there was no treatment at all with a system like this, and nothing to stop pathogens from breeding and infecting the soil around the tank, or even penetrating aquifers and watercourses.  I helped dig one out many years ago, and all the soil around the thing was deep black and exceedingly smelly.  We dug out all the soil for around three or feet away from where the old brick lined tank had been, and spread it over a field, where it will have gradually been made safe by normal soil bacteria.  Not a pleasant job, it has to be said!  We replaced it with a Klargester "onion" septic tank, with perforated pipe land drains in pea shingle filled trenches running away across the adjacent field.  That's still apparently working, but it's 20 odd years old, so my guess is that it's really just draining raw and untreated effluent into the field by now.

A proper septic tank will be sealed and will have a drain (or drains) coming from near the top running out to relatively shallow land drains.  Nowadays these land drains will be perforated pipe, but older ones either use unjointed clay pipe sections, with gaps between the joints, or field-type land drains with just a trench filled with stone or hardcore.  All these forms of land drain stop working after a few years, in terms of treating the effluent, but there won't be an outward sign of this, the effluent will still drain away it will just remain septic in the deep soil, where there's not enough oxygen to allow aerobic bacteria to treat it and make it safe.

Sounds like your "brick lined chamber" suspicion. Just had it confirmed what it is. Speaking to the previous owner tonight (he's 87 btw), it was "a big hole dug in the ground in 1953". The builders apparently "mixed up the cement in the bottom of the hole and bricked up the sides.....then broke up the cement on the bottom,,,,,and put a man hole in the top".

[ProDave]

I think your best course of action is a new treatment plant in a new location with a new soakaway. Now whether you have enough room for that is another matter, but I think you can be sure the ground around the existing tank is going to be pretty dire.

[Onoff]

Back to the original thread.....

 

Got my trench dug (at the 750mm min admittedly). Plus got everything I need to run the new main.

 

At the mo mains in is via the old rusty main comes up from the road then connects to a bit of 25mm MDPE halfway. Then at the house back to iron where there's still a slight leak (I chop back and re-make then it gives up not long after). This was a mistake. I'm totally ditching all the iron and running a completely new, one piece length down the trench.

 

BUT.....holding off as wondering whether I should in fact run the 25mm MDPE in it's own protective 50/63mm blue, corrugated duct. Although I'll be bedding and covering it in sand I'm thinking this:

 

http://www.plastics-express.co.uk/ducting/twinwall-duct-coils/blue-twinwall-duct-63mm-x-50m-coil-p-pm403

 

- The ground is very flinty and full of roots. 

- I'll be laying the MDPE maybe touching the rusting old iron pipe in places and even crossing it, as it doesn't quite follow the original route.

- The new pipe run passes a rough (rain water) soakaway on the right. You can just see the 4" soil pipe going into it. Tbh this has never been connected and in fact we broke the section running up to the house with the digger.

- Beyond the line of jumbo bags in that clump of bushes and next to the fence is the (still in use) "bottomless pit" cess pool type thing.

 

 

 

 

[Onoff]

Thought it best to bring the 25mm MDPE up through the suspended floor in an insulated duct (as I believe you're supposed to). So after a bit of pi$$ing about making an extension for a core cutter I drilled through the footings. I had to drill a bit more than the 250mm shown as there's some sort of brick detail at the foot of the wall.This is roughly the section I have:

 

I have some 63mm OD ducting which has an internal diameter of approx 50mm. Gives me nom 1/2" all round to add a bit of insulation:

 

 

 

So I now need to:

 

1) Insulate the MDPE

 

2) Protect the duct in the floor space

 

3) Get it in!

 

Thinking maybe normal, grey pipe lagging.....22mm? Maybe some thin stainless mesh / gauze rolled to fit round the duct for protection?

 

Any better ideas? Cheers

Edited September 18, 2016 by Onoff

[Onoff]

Reading a bit more today and it seems I SHOULD have used a 100mm duct!

 

Too much grief so this 65mm one is going in.

[Oz07]

If no inspection by water board then don't worry your duct size will be fine. If it's thru it's thru

[Onoff]

33 minutes ago, Oz07 said:

If no inspection by water board then don't worry your duct size will be fine. If it's thru it's thru

 

Water board bloke just said to take photos of the trench.....

[ProDave]

MDPE is okay buried in the ground. It's what Scottish Water do here. The only duct is where it passes under the road.

 

I see my neighbour is having "issues" with SW. they have refused his connection. One of the reasons being he put his toby too far from the road.  I wonder if the fact he put the water pipe in a black duct under the road is the other issue?
 

[Oz07]

Water board are notorious for finding something wrong with what you've done. Or something additional for you to do. In your case I gather you already have a water supply so don't need them to approve before you connect?

 

anyway take photos of the trench, tell him it's 4" duct and where you bring it up into house use a bit of 4" drain   

[Oz07]

Ps well done on the art work don't show heritage England!

[Onoff]

Existing iron main so trenched down to that depth which is nom 750mm. 

 

Gone with a metre of 22mm pipe insulation over the MDPE duct taped to close the split. Shoved up the 63mm duct:

 

 

 

Getting it in will be fun!

 

Found this galvanised thin gauze that I reckon I can roll into a nom 65mm dia cylinder to go round the duct where it comes up into the suspended floor:

 

 

Would have preferred st/st.....

[PeterW]

52 minutes ago, Onoff said:

Would have preferred st/st.....

 

Just how sharp are the teeth on those tunnel bunnies of yours..??!!

[Onoff]

16 hours ago, PeterW said:

 

Just how sharp are the teeth on those tunnel bunnies of yours..??!!

 

For its better corrosion resistance not mechanical strength!

[Onoff]

Must try this weekend to finish getting this MDPE new main in and do away with all the temporary fixes along the run. Weekends of late.....well haven't really had them due to other issues.

 

So, trench dug. Everything I've read says to line the base of the trench with "sand". Should that be soft/ sharp or even ballast. I'm guessing soft. No problem ordering in a couple of three jumbo bags. In the very flinty ground I have is soft sand "enough"? I'm still tempted to just order a length of blue duct and forget the sand. I could then just backfill without worrying too much about damaging the pipe. Would it negate the need for sand? Cost for a roll of duct vs the sand, there can't be much in it!

 

Any thoughts?