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Let me take you with me on my first steps on the road to cynicism in the building sector.

For some reason (sewage smells?) many people appear to delay attention to the soft and smelly until it’s either too late or until they’ve backed themselves into the smallest room in the house; and then, trousers round their ankles, they allow someone to lock the door from the outside.

Evidence? Use the search terms refusal and percolation on our LPA website. ‘Refused pending percolation test results’ is all too common.

Imagine then my incredulity when, on the recommendation of a colleague, a company turns up to do a ‘PERK test (mate)’ for a drainage field on our land.

Just a bit of context…. we live in sight of what was a clay quarry, within cricket ball throwing distance in fact So, there might just be a bit of clay around 

“Yeah, that looks fine (mate) you’ll get a drainage field on here no bother” he says without so much as lifting a shovel.

“Tickety boo ” I say. “Gonna do the percolation test then?”

“Aye… I’ll get ‘t shovel from ‘t van”

“Where’s your machine then?” I ask. “No need for one (mate)”

“I’ll get the tea on then” . Tea duly made…. yer man’s gone

A square foot of the turf has been gently disturbed in one spot, and carefully replaced.

An alarm bell sounds in the dim, dark recesses of my brain. And instantly switches off. Time for the pub.

Friday is International Party Night in our place.

Monday – Here are verbatim copy and past unedited (anonymised) passages from the written report;

…I can confrm [sic!] that we have carried out a porosity test to determine the suitability of the sub soil. The percolation results indicate that an excavation area of 23m2 for the sub surface irrigation system is required….

…Condition of soil: Loam soil to the base of the excavation….

…Number of excavations: No.3 trail [sic!] pits to a depth of 550mm….

…Percolation values: Pit 1 – 16 secs/mm.

Pit 2 – 20 secs/mm.

Pit 3 – 19 secs/mm.

Average percolation value: 19 secs/mm….

(Condition of soil: Loam soil to the base of the excavation.)

The briefest look at H2 Drainage Fields and drainage mounds page 31 to 33 shows the requirement for hole to be dug to 300mm below the intended invert (para 1.33 page 32). In our case that would be a two meter deep hole at least.

So, trying to be fair, I suggest to the company that I pay for a properly constituted percolation test.

Here’s part of the emailed response from the company

. ..However [our report] would be based on the procedure we carried out [reported in the quotation above] to confirm the first report which we have done 100’s of times and never been questioned by Building Control/Planners once.

Talking to a different company rep about the matter and he grins disarmingly.  And tells the story of a completely built house without access to either off mains drainage or a sewer. Off-mains drainage can be a show-stopper, not a lot of people know that.

If like me you aren’t a builder, there’s no substitute for reading and reading and reading.

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This brings to mind the old adage about professionals vs. amateurs:

"A professional does the worst job he can get away with; an amateur does the best job he can".


I did my own percolation tests and my results showed that I couldn't successfully use a normal soakaway system, so I ended up ploughing about 17% of my total project cost into a proprietary drainage solution.


Perhaps if I had contracted this whole thing out, I would have found a 'bloke with a shovel' who would have written whatever numbers he felt were best on the form, and then built me a conventional system... which would have backed up in the first rainy spell and left me with effluent flooding out of the ground. Mmm, nice!

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