Sewage not flowing correctly?

[Pieinthesky]

We are having a granny annex built and there is a sewage run about 15m long from the toilet in the annex to the existing inspection chamber to which it has been joined.

When they were connecting the pipe I could clearly see that it was sloped upwards as it came into the inspection chamber. I stopped them working and got the boss out who made them dig it up and level it correctly. Thats what he said!

Having lost a lot of trust with the builder I wanted to make sure the pipe was correct so today I tried a couple of tests:

Test 1

I poured 1 litre of water in at the toilet end - nothing came out at the chamber
Another 1 litre - nothing came out
Poured in a third litre and about 1/2 litre came out the other end - it trickled rather than gushed.

Test 2

A couple of litres of water with 4 slightly past their best potatoes and a couple of handfuls of bog roll mixed in were tipped into the soil pipe where the toilet will be. Some water comes out the other end but no potatoes or toilet roll.

I then tipped a gallon of water down as fast as I could to try and flush everything through. No solids appeared

I am not an expert but it seems to me that if this is left as is, we will forever be having blockages.

Am I correct? should I have the builder dig it all up again?

I think I know the answer but would very much appreciate the opinion of someone who knows about this stuff?

Thanks

Mike

 

[mikeey84]

I think you know the answer. Get the boss out and run the test with them

Also, putting potatoes down a sewer pipe is probably not a great idea

 

[Pieinthesky]

Potatoes were the best thing we could think of - don't think they can do much harm can they?

If small round spuds won't flush through - my jobbies have no chance

 

[bernardgreen]

Sounds like your builder qualifies as a block head.

 

[noseall]

I think I know the answer but would very much appreciate the opinion of someone who knows about this stuff?

Laying drains with a minimum of fall is a pain, that requires skill and patience. They have to be laid to perfection (and to a taught line) with zero dips. You have to be careful even when back-filling. We laid some with just a shade under half the recommended fall and they still work perfectly to this day. We use the site laser when judging the falls available and work accordingly.

Sounds like your builder does not give a chuff and was relying more on the 'fingers crossed' method rather than skill.

Standard foul drain falls are 1:40, but plastic drains can be laid to half that and work fine. A 15m run, to standard falls would require about 375mm of fall.

 

[Pieinthesky]

Thankyou noseall

We had very limited fall so rather than risk getting into problems we have installed a pumped sewage tank - at the end of the 15m run.

So they shouldn't have any problem getting sufficient fall !!

 

[Hugh Jaleak]

Drain laying was once an art, in days gone by, the Sanitary Inspector would attend to view a completed drain run, and to test it, he'd roll a ball down the line. If it came out the far end, all well and good, the run passed. If it didn't, not only did the Drainlayer have to explain why not, he also had to find and retrieve the ball.... Now it seems acceptable to cobble any old arrangement together, after all the groundworks team will usually be long gone by the time the Occupiers realise there is an issue with the drainage system.....

Drains must be laid with an adequate fall. A 'Self Cleansing Velocity' is often mentioned, i.e. the waste needs to travel at an appropriate speed to get away. Too slight a fall and the solids can sit in the pipe whilst the water trickles away, too steep and the water can rush off leaving the solids behind. Seems you have the former.

Get them back, if they argue the toss, get a third party independent to CCTV the drain run, if there is anything lying in the pipework, ask the Builder to explain why!

 

[Pieinthesky]

Thanks Hugh

I think we have the correct fall in theory, I suspect there are some undulations though.

 

[Old Salt]

Thanks Hugh

I think we have the correct fall in theory, I suspect there are some undulations though.

And that is the whole point, if there are undulations it has not been laid properly!

 

[Hugh Jaleak]

I think we have the correct fall in theory, I suspect there are some undulations though.

Afraid you can't have one or the other, if it's laid to the correct fall it will work. If you have 'undulations', it won't.

Simple as.

 

[Pieinthesky]

And that is the whole point, if there are undulations it has not been laid properly!

I fully understand that and have spoken to the builder - he says he is going to check it and sort it out.

I will let you know how it go's

Thankyou everyone