The case of the mysterious septic tank

[HVB]

Well it's not that mysterious but I was hoping to draw a crowd...

Throwing caution to the wind, we moved house recently. In any case, we now own a septic tank - a new experience, of which I know very little.

The previous owner, a little old lady, lived here on her own, but had the septic tank emptied twice a year. At almost £200 a time.

Even with my limited knowledge this seems a touch excessive and so a thorough investigation into septic tanks and what to do with them was on my to-do list - just not as far up the list as decorating. I planned to look into it in the new year.

However... the waste contractor turned up unannounced the other day to empty the septic tank (and relieve me of £200).

As I hadn't asked him to empty it, I politely told him that I didn't want it emptied as it probably didn't need to be done.

Sensing weakness, he suggested we go and have a look... he lifts the cover and there's liquid up to some sort of collar-device near the top of the tank and evidence that it has been higher into the 'tube' at some point. "Look - it's full", he proclaims.

Not knowing much about it, but certainly not wanting a blockage, I allowed him to empty it - which took just a few minutes. After he'd finished, I had a look into the tank and I could see the bottom, so at least I know it's empty now.

The tank is about 12 years old. Lifting the cover reveals the main bore and two smaller pipes, which at a guess are vents. From the limited view I had, I would say the tank is one of those GRP ball types with a vertical tube out of the top.

Researching the septic tank FAQ, the archives of this group and furious googling, suggests that:

- emptying twice a year is excessive

- £200 is steep for emptying it

- in normal operation the tank would have appeared to be full anyway and this isn't a sign that it needs to be emptied

Is the above correct?

How do you know when it needs to be emptied? I'm obviously keen not to get 'done' but at the same time, I don't want to cause future problems by skimping on essential maintenance.

Views greatly appreciated.

HVB.

[Peter Taylor]

I think we first need to clarify whether it's a septic tank or a cesspit. Septic tanks don't normally need emptying (except VERY occasionally when it needs cleaning out). The effluent is treated in the tank and discharges into the surrounding soil via underground drains. OTOH, a cesspit is just a tank, and needs to be emptied when it gets full. If you can see an outlet pipe in the tank, often with the end pointing downwards, it's probably a septic tank. Also look at the ground round the manhole cover - is it lush green? :)

If it's a cesspit, the frequency of emptying depends on its size and the amount of effluent. You can probably find equations on the 'net to work it. Have a look on the Klargester site. Twice a year doesn't sound too bad, but £200 does seem expensive so I think getting some alternative quotes is a good idea. And don't forget you can get a rebate on your water rates for the disposal part.

[Broadback]

I have mine empty every five years. The cost using a proper company, who give me a certificate to say that the effluent will be environmentally disposed cost £108. It is a modern tank installed about 4 years ago, replacing the original concrete one. Looks like a very large fibre glass flask, not that it can be seen now as it is buried.

[Peter Taylor]

PS Septic tanks are always full - that's the way they work.

[robgraham]

Just to add in my pennyworth, and it may well be that you have found this already. Septic tanks come ,as far I know, in two flavours - the modern ones in GRP, shaped like a bottle - and the old fashioned brick /concrete ones, often in the form of a double tank. The advantage of the latter is that because of their sheer volume, they are far more tolerant to the abuses of extended emptying and excessive loo cleaner usage. My understanding is that the modern ones, because of their 'well' design volume, do need emptying every couple of years and care needs to be taken with sanitary chemicals, etc.

My elderly one happily lasts 10 years + before conscience drives me to get it pumped out, and don't tell anyone, but the outlet finds it's way to the local burn. This outlet did block after some 60 years of life, but then it was just field drain pipes so it was hardly surprising to find it full of soil.

Rob

[Dave Liquorice]

Yes, for a septic tank. If it was a cesspit you'd probably be looking at less than monthly depending on it's capacity and how much volume you put into it.

Correct. There are plenty of places on the web that outline how a septic tank functions.

Only real way is to dip the depth of the sludge in the bottom. You don't want the sludge to get to the bottom of the outlet dip pipe. Again how to dip the sludge is on the web, involves a stick long enough to reach the bottom of the tank, wrapping it in cloth and shoving in down to the bottom of the tank. Then withdrawing carefully and inspecting to see if you can see the transition from fluid to sludge.

[Huge]

We've lived in a house with one for over 15 years, now.

Yes.

We get ours emptied once a year, and some years we forget, so it goes 2 years, and we pay under £100. It's always full of liquid, except immediately after emptying.

[Huge]

Ick.

[HVB]

I'm fairly certain it is a septic tank. It's a small-ish bottle type tank, looking very much like the Entec Alpha Septic Tank, though without the baffle - see:

If you can see an outlet

I can't say that I can see the outlet, but from all appearances suggest it is a septic tank rather than a cesspit.

No, it's not but that's probably as much to do with the fact that there's lots of shrubbery around.

The other reason I suspect that it's not a cesspit is that there is a public sewer within easy reach of the plot. I suspect that the septic tank was put in to save money over the longer term, rather than paying the regular sewage charges.

I know strange things happen, but I can't imagine why someone would bother to put in a cesspit, with the regular emptying requirement, when they could simply have connected to the main drain for a one-off charge.

Ta - will do.

Yep, already checked that - I know from past arguments with the water company that the sewage charge is the expensive bit.

HVB

[HVB]

[on septic tanks]

Hmm... that's interesting. Is the certificate a requirement?

I didn't get one for my £200, so I guess I can't say for certain what has been done with it. I hope he didn't just empty the thing into the nearest convenient ditch.

HVB

[HVB]

We're on the side of hill and the plot is an odd shape. I suspect that if the drainage field is damaged there aren't going to be any alternative locations available to me (unless I can dig up next door's garden...).

Usefully, there is a public sewer running down the middle of the road fronting the property. If it comes to it, we could probably negotiate access to that - though I gather that can be an expensive job in itself.

Good idea - I hadn't thought of asking the building control people - there was barely a mention of it in the property deeds, just the location of the tank. As for the neighbours - they are connected to the main public sewer!

Done - but thanks anyway!

HVB

[HVB]

Noted - thanks.

[HVB]

Ours is definitely of modern design. Your comment about the sanitary chemicals is so obvious that it simply hadn't occurred to me.

In fact, the previous owner left us a "gift" of an arsenal of cleaning products (more than we would buy in 10 years... I probably should have called a hazmat team in - heh!). I have a sneaking suspicion that she may well have scuppered the natural break-down processes and perhaps that's why the tank needed frequent emptying.

Wow! That's much more like it. £20/year sounds like a bargain. ;-) Sounds like twice a year for emptying is way too often.

Thanks! HVB

[HVB]

Sounds reasonable. I'm guessing that with average use (3 people) it would take a fairly long time to actually fill the thing up with sludge - I'm the only one that's ever accused of being full of s... :-D

Thanks - I hadn't found that anywhere I'd looked. Sounds like a right lovely job.

HVB

[HVB]

Thanks Huge - that's more like what I was expecting.

HVB

[Gel]

If your Council (or a neighbouring one*) still offers tank emptying, they'll always be most competitive.

*We live on border and though our Berkshire Council stopped service some years back, neighbouring ones in Oxfordshire didn't and will cover adjacent areas.

[Huge]

[Reformatted to usenet norms. Please do not top post.]

That's who we get to empty ours.

[Andy Dingley]

Cesspits need emptying, septic tanks process the waste, drain the effluent and don't.

You shouldn't need to get a septic tank pumped out more than once in a blue moon. Twice a year means something is broken, or at least unnecessary.

If it's "12 years old" and made of fibreglass, that's going to be intended as a septic tank, not a cesspit. Cesspits are obsolete, fraught with regulations, and generally unnecessary unless you're planning to live on top of Rockall. If you're having to empty it, then something is knackered. You can convert a septic tank into a cesspit (unintentionally) by knackering the outflow. You can convert a good septic tank into a bad one by killing the bugs. This won't cause it to fill up on its own, but it will stop digestion. There's then a (small) risk of bunging outflow pipes and we're back to the impromptu cesspit.

A local farmers' shop (great places for wellies and baler twine) will sell you bacteria re-stocking powder. You shouldn't need this regularly, but it's great for re-populating if you have ever killed or emptied it. Using Ecover for washing and laundry helps too - if you have an above-ground coke bed as the final stage (1950s-1970s tech), put it on a low phosphate diet (laundry powder) or else you'll have to start weeding the thing!

If you download a few makers' leaflets, you'll see what the liquid levels are intended to be. A septic tank always operates by being more or less "full" though, as the fluid has to flow over the weirs into the next stage. If you leave a fibreglass onion empty and it rains, then it may even try to float! (search "Night of the zombie septic tanks"). By the sound of it, assuming you've no _real_ problems, then you're just being charged to empty something that shouldn't be emptied.

=A3200 is reasonable if you're remote and awkward, but =A3120 is more like it round here.

If you've reliable power to hand, no slope and no space, then Klargesters are very good.