House with septic tank under drive

riverboat2001

We've found our "perfect" house which fits every criteria we drew up.
It was built in 1980.
We put an offer in, and it was accepted, we had a level two homebuyers report carried out which effectively said it was connected to mains drainage.

However, there is apparently a septic tank built under the driveway.
The vendors have lived there for six years and have said they have it emptied every two years.

The driveway is block paved and has a heavy duty manhole cover in it.
The driveway leads down to a huge double garage.
My issue is I want to drive a 7 ton motorhome onto this land.

We had a second viewing yesterday and there was a whiff coming from the manhole area.

Is it likely to be built strong enough to withstand something heavier than your average car?

Davesnave

riverboat2001 wrote: »

We had a second viewing yesterday and there was a whiff coming from the manhole area.

Is it likely to be built strong enough to withstand something heavier than your average car?

It is very likely that a septic tank situated in a driveway, all built in relatively modern times, will be able to take the weight of your motor home, especially if it was built along with the property. The building process would have seen heavy lorries traversing the driveway.

Some tanks are onion-shaped and have a very narrow top, so there is not a large space to span. Others, which are basically brick chambers, will have a reinforced concrete top. If the tank is a replacement and went in more recently, it could be plastic, like an oil tank, but again, installation would have taken account of location and the existence of HGVs.

Remember the weight of your motor-home is spread between the wheels; it's not all applied at one point.

The essential thing to find out is what condition the tank itself is in, so you may need a specialist survey. The whiff you mention is fairly normal, although there will be others along later claiming their tanks don't smell! Part emptying every 2 years is good practice, and again, others will possibly disagree, but not all tanks are the same size or used in the same way.

AdrianC

riverboat2001 wrote: »

We put an offer in, and it was accepted, we had a level two homebuyers report carried out which effectively said it was connected to mains drainage.

That's really not for an HBR to say. The definitive answer to whether there's mains drains available is for the utilities surveys that your solicitor will be doing. Or you could just ask the vendors if you can look at their water bill...

However, there is apparently a septic tank built under the driveway.
The vendors have lived there for six years and have said they have it emptied every two years.

OK, so we can probably rule out mains drains.

The driveway is block paved and has a heavy duty manhole cover in it.
My issue is I want to drive a 7 ton motorhome onto this land.

A single corner of the motorhome (do you really mean 7.5t? That's a big motorhome. Truck chassis. US RV?) won't weigh 7.5t, of course, and you're not putting the whole lot on the manhole cover at the same time. At a guess, you're looking around 5t kerb weight, and that's probably 1:2 rear:front, so the most on any one corner is 1/3 of the total weight - less than 2t. Plenty, but well within the capacity of even the cheapest non-pedestrian-only manhole cover.

We had a second viewing yesterday and there was a whiff coming from the manhole area.

Specialist survey time!

Is it likely to be built strong enough to withstand something heavier than your average car?

<shrug> It certainly SHOULD be. A 7.5t truck is not unforeseeable for the average driveway - I bet the builders had the same, if not larger, up and down there when the garage was being built, for a start... And if your removal wagon uses the drive...

moneyistooshorttomention

Well - they've lied about the mains drainage. Hmmm...

I would be sceptical about having such a heavy vehicle parked permanently on the drive. The occasional "heavyweight" (eg removal van) is one thing. On a regular basis is quite another.

I've certainly read (and tried to understand - ahem...) technical specifications about roads and manhole covers before now. There is quite a bit of information there on the Net about what weights different types of road and different types of manhole will take.

Prior to that - I just thought "a road is a road and a manhole cover is a manhole cover" - and then I started reading through that and thought "Not so - according to this" and various vehicle weights were being specified for various types of road/manhole cover.

I suggest you google for that sort of technical information and study it in detail.

marksoton

Does the MH cover have any markings?

You're looking for a class D400 ductile iron.

However as Dave points out the integrity of the structure beneath is probably more important.

As for the smell, you could install a sealed cover.

DaftyDuck

Money .... NOBODY LIED!!!! I do wish you'd lose the accusatory attitude. It was the surveyor who was mistaken, owners state emptied every two years... No lies there!

OP: your searches will show if mains drainage is available. If it is, you may well choose to connect to it, and can therefore fill in the septic tank. Problems over.

If not, and the tank must stay, it's pretty easy to have a professional strength assessment of the tank, and reenforce if necessary.

However, a simpler approach. It was a block paved drive, with a double garage. Do they use the drive and or garage for cars? Was there ANY surface deflection around the tank area, any puddling in rain? If so, there may be some weakness. If not, you are probably OK. Check where the tank actually is, as it may not be directly under the drive.

As has been pointed out, the weight of the camper van will be spread, and may not be as damaging as you might imagine.

arbrighton

Surveyors and even architects rarely actually understand septic tank systems- I have anecdotal evidence of this at our place. Ours is not a modern one- built around 100 years ago. Vendors were totally open about it and repairs done on pipework thanks to tree roots. Surveyor was specifically asked to comment on it for a full building survey but they clearly didn't understand the basic principles of tanks rather than cess pits based on their report. Oh, and the architect. Didn't understand that we really shouldn't drain the surface water through the tank.

Really must book to get ours emptied- regardless of whether it needs it, thanks to an arrangement with Canal and Rivers Trust, I am obliged to have it done annually (yes, I'm that close to a water course)

No idea about the motorhome though, sorry..

davidmcn

moneyistooshorttomention wrote: »

Well - they've lied about the mains drainage.

Where does the OP say that?

The surveyor assumed it was mains (in the way they tend to do e.g. "we assume the property has mains drainage/water/public road [because we haven't seen any evidence to the contrary] but you should get your solicitors to check"). Even if they spotted the septic tank they wouldn't have said much more about its condition or weight-bearing abilities unless there were already visible problems.

riverboat2001

The Motorhome is 6990KG its an uprated twin rear wheel vehicle.

The local water company have said that the mains is right outside the front of the house, and a connection would be possible. However as the kitchen and the bathrooms are at the rear of the property I don't know how easy or feasible that would be.

I fully intend to get the tank checked, as I'll have to use it while I save up the money for the connection.
The block paving all over the drive has no dips or bumps, and doesn't look to have been disturbed in any way.

The House is built on a slope, so the front of the house is at street level, and the garage is right underneath it at the back, the driveway slopes down the side and round to the rear of the house to the garage.

I've just spoken on the phone to the company and operator who emptied it in July and he said it's a 1000L Klargester bottle, with the top of the tank abut 1 meter below ground, and the bottom of the tank is approximately 2.50m down.
He said the tank is in good condition and he drives a 30t vehicle down the drive to empty the tank!
It has put my mind to rest, I will however still get a specialist survey, so I know myself how it all works, and where exactly it all is.
Something that I'm surprised that the present owners don't know.

AdrianC

riverboat2001 wrote: »

The Motorhome is 6990KG its an uprated twin rear wheel vehicle.

6990kg GVW, I presume, rather than kerb. If it's kerb, you're going to need to pack light or have a big licence.

riverboat2001

AdrianC wrote: »

6990kg GVW, I presume, rather than kerb. If it's kerb, you're going to need to pack light or have a big licence.

Yes that's GVW