Septic Tanks and winter water levels

[stefan]

I'm having trouble with our septic tank and need a little help weighing up the pros and cons of various solutions. It's a brick construction - from 1973 I think. It's worked reasonably well in the 3 years we've been here but recently I've noticed standing water (and worse) in the inspection hatch near the house. We had the sludge drained last year and it's ben rodded to check for a blockage in the pipes.

We're having a small utility room built and this will add a downstairs toilet and washing machine to the system. The builder isn't convinced that there is enough drop for the toilet to function properly (and definately not if there's standing water). There seems to be very little fall in the system altogether - the inlet is perhaps only 50cm deep.

When we dug the foundations for the extension they quickly filled with water to a depth of approx 50cm below ground level.

My theory is that with the winter water table so high and the soil being clay the soakaway cannot function properly - it may even be under water!

As I understand it the options for me are...

1) Add a sewage treatment unit to the tank and expel the clean water into a ditch at the end of the garden. £2000?

2)Get connected to the mains sewers - approx 50m away. The drop may be an issue again.

How would the costs compare? Have I overlooked any other alternatives? What can I do if I haven't got a very good fall to the mains connection - can I use a pump? Is it worth digging up part of the soakaway to see what's wrong with it before I give up on it?

Thanks for any help.

 

[Nemesis]

I'd first of all check your soakaway - it could well now be very clogged and unable to function.

 

[stefan]

Is that something I do by digging it up or do I need someone with a camera?

 

[Nemesis]

If you know where it is, you could uncover a part of it. They can eventually clog and simply stop draining... especially on clay.

In the long term if you can afford it I'd look carefully at your other options. You can pump stuff to the mains, yes, and yes if you have a suitable drainage ditch in which to put treated outflow that's worth conmsidering too.

We have a small septic tank on not too free draining soil and you have my sympathies! We think the mains is a little too far, but are looking at the treatment options.

PS - have you looked into the tank itself, to see if it's full over the outlet, or if indeed stuff is draining eventually?

 

[stefan]

Thanks for that. I've just spoken to a place called Amos pumps - they recon a suitable pump to connect to the mains woud be about £1470 + the pipes and groundworks. A similar cost to adding a sewage treatment system but I think it could be less hassle.

Hope you get yours sorted.

 

[Nemesis]

Ours is OK as there are only two of us, but for the size of house for future residents I think it wouldn't be acceptable really, most people use far more water than we do!

If you can connect to the mains then it's a good plan, although check out running costs of pumps etc.

We would have to pump sewage uphill to reach the mains which I think might be hard work for a pump.

We have been looking at a treatment installation which sounds useful:

http://www.biotank.co.uk/


It would be interesting to know what other people have found works well.

 

[MdB]

The downside of connected to mains drainage is the increase in your water bill. If I remember correctly, the sewage charge is calculated on something like x4 or x5 of your water charge. Your water bill will therefore increase by x5 or x6 if you connect yourselves to the mains sewage system.

edit - incorrect figures above, see following post.

 

[Nemesis]

We reckon that emptying costs etc more than make up for any cost saving re sewage charges! It wasn't a vast sum last time I checked that we saved. It's something to factor in though if a treatment tank can be considered instead.

On clay soil many tanks simply can't do the job for a septic tank nowadays.

 

[stefan]

There are pros and cons to both systems. I'l have to add up the exact figures later. One of the plus points of being connected to the mains would be that I'd get a large part of the garden back - we'd like to put a pond in but can't because of the soakaway. The other big plus point is that we'd be able to finally get a decent fall in the waste pipes. We couldn't do this if we kept the current septic tank and simply added a sewage treatment device.

It's looking like for us, mains is the way to go. I'll post the figures involved anyway - it might be useful to others looking into running and installation costs of the various solutions.

 

[alice]

This might be a silly suggestion....but if you can limit your solid wastes and only have to deal with grey water, would it be easier to configure? What about composting toilets?

My sympathies on the septic problem. We have a septic system here at my house in Texas, and the soil here is very compact. Last year my mother-in-law with Alzheimer's came to live with us for a brief time. We hadn't realized the extent of her illness and left her alone at home during the day while we were at work. While alone, unknown to us, she ran the water in all the sinks constantly. One day I was walking out side and walked over the leachfield and sank up to my ankles. I also noticed a pond forming in the back yard. She had saturated the leachfield and somehow our tank got clogged with all sorts of items that should never had been put in it. Turned out she did a lot of flushing of things like rags, etc, as well. It took us months to empty the tank and dry out the field. Eventually we were able to get it sorted out, but oh, it stank and the water attracted mosquitoes and vermin and it was nasty for ages.

alice

 

[stefan]

Thanks Alice - I won't ask how you were thinking I'd limit my solid waste
Sounds like you had quite an adventure there. It may be a bit late in the day to think about composting toilets - from the little I know it seems that they're better suited to a green new-build than fitted into an existing traditional building with limited space. No doubt someone will prove me wrong.

 

[Nemesis]

Live on beer?

 

[charlie-ia]

"we'd like to put a pond in but can't because of the soakaway."

Are there any reasons why a raised pond coudnt be built ontop of a soakaway?
would the weight be too much and crush the pipes? i suppose if the pipes had to be removed later it would be a bit of a bind.

whats the expected lifespan of soakaway pipes?

 

[stefan]

We didn't really want a raised one as it's a bit exposed. But we were also worried about access to the pipes - or access should we ever have to lay a new soakaway.

 

[Penners]

Your water bill will therefore increase by x5 or x6 if you connect yourselves to the mains sewage system.

No - surely not. In our last house we had a septic tank, and I reckon that roughly halved our water charges, compared with being on main drainage.

I'm sure that connection to mains drainage won't increase your water costs by a factor of 5 or 6.

 

[MdB]

My memory did not serve me very well (though I can't find an old bill quickly to check) but the South West Water site suggests that the sewage charge is around 1.6x the water charge (exact figure depends on usage). This means that connecting to the mains sewage will increase your by a factor of 2.6. i.e. a £100 bill will become £260.

 

[Jane Smith]

Could be the tank's brick contstruction taht's causing problems: it allows groundwater to seep in, which can flood the whole system. You should consider replacing it with a plastic tank.

As for a pond: well, you could replace your soakaways with a reed bed system which work well as a secondary treatment method. Not exactly a pond but a lot closer to one than a buried soakaway.

 

[stefan]

That's true - that could be another cause. Thing is - looking at the modern plastic septic tanks with their 1m deep outlets - that would pretty much guarantee the soakaway would be submerged.

Costwise I think a new tank and soakaway (or treatment system) will be more expensive than connection to the mains with a pump.

 

[Lime]

In the Anglian region the sewage charge is based on water consumption or water rates.
It is around about the same as the water rates thereby doubling the bill.

 

[Jane Smith]

We put in our own septic tank and soakaways for about £1,500 in 2002: it took about three days with a digger and driver, and my husband to do the manual bits. Quotes for drainage companies to do the same job came in at £10-15,000. That cost involved the new tank, the aggregates, the piperuns and the digger hire. It's all still working very well.