Finding a blockage in a 50mm mdpe pipe ?

[ProDave]

Today has not been a good day.

 

Our old house has a septic tank with a pumped output up to a soakaway in the field behind.  Tenant informs me there is a "problem"  The pump is not pumping.

 

So I go and fit the spare pump. Pump runs, but the water level does not go down.  Uncouple the flexi pipe and turn the pump on, it pumps water.  Conclusion, there is a blockage. The pipe from the pump chamber to the soakaway is 50mm mdpe.

 

So tomorrows fun job is to try and find the blockage.  Any ideas how?

 

I think the first step is locate the pipe where it exits the garden into the field. I have a photograph that pinpoints it's location almost exactly in the middle between 2 fence posts.  I don't think it is especially deep there.  If we can dig by hand and find it then what?  To cut it with the intention of re joining it, would need a lot of pipe to be exposed to allow the 2 ends the be pulled apart to get a coupler in.  So my thought is drill a small say 4mm hole in the pipe then turn the pump on.  If the pipe is clear to that point we get a fountain and I can then seal the hole with a self tapping screw and some sticks like sh*t.  No fountain and it means the blockage is closer to the pump chamber and we try again closer.

 

I can't see how a 50mm mdpe pipe that is only transporting grey water can actually block, so my fear is a problem where it joins the actual soakaway.

[scottishjohn]

how far from joint you can remove to where it joins soakaway --have you a long length of smaller  plastic pipe 

 

try putting small pipe  down 50mm pipe and see if you find a blockage ?,even better if you can connect a mains supply to it if it is blocked to flush it   ??

could it be fatberg?

 

https://www.orrplumbing.com/blog/2015/may/what-is-a-septic-tank-grease-trap-/

Edited February 15, 2019 by scottishjohn

[Russell griffiths]

Your an electrician, can you lay your hands on one of those fibreglass cable pulling things on a roll like the telecommunications guys use. 

Poke it in have a hunt. 

[scottishjohn]

something I have been contemplating for my septic system 

wife insists she never puts fat down sink at present house --but I know different from what i found in drains a couple of years  ago 

thiking it might be good addition to add to drains before it goes to  septic system 

you have tennants- do you think they will be that careful?

Edited February 15, 2019 by scottishjohn

[scottishjohn]

I was lucky the self propelled drain jetting extension on power wash did it fine 

a good add on for the karcher.

as is the wet sand blasting attachment --cleaned rust off my stone work of my chimney stack from an old tv mast that the dipsticks attached with mild steel clamps 

Edited February 15, 2019 by scottishjohn

[ProDave]

This is the grey water OUT from a septic tank, so it won't be a fatberg, all that and various solids get contained or dealt with in the septic tank and the bi annual pump out (it was pumped out last summer)  likewise toilet paper and womens products won't make it to the pump chamber.

 

It's a 50 metre run from the holding tank to the soakaway. Longer than my cable fish rods.  

[Russell griffiths]

Do you know if there are any joins in it. 

Tree roots ??

[scottishjohn]

how old is system 

[epsilonGreedy]

If I ever appear on MasterMind my specialist subject will be "unblocking yacht holding tanks".

 

My first suggestion would be to apply some air pressure to the far end of the pipe i.e. in the reverse direction to the normal pumping action. From experience it is surprising how some feeble squishy solids can coalesce and form a plug that fights high pressure in one direction and yet some gentle pressure in the reverse direction causes the plug to disperse into a cloud of nothingness.

[ProDave]

It's 15 years old. No joints, one continuous coil of 50mm mdpe. It was me that installed it when I built the last house.

 

I thought the rule on a yacht was "He who blocks it  - Unblocks it."

[scottishjohn]

could it be that the drainage filed has just blocked up over time ?

seems very small dia pipe at 50mm 

are the perforated pipes same dia ?

my thoughts for mine when i do it is a lot larger than that  as i have read that under certain circumstances 15 -20years could be life of drainage field 

I want to fit one that will be still going when they plant me

 

Edited February 15, 2019 by scottishjohn

[epsilonGreedy]

7 minutes ago, ProDave said:

I thought the rule on a yacht was "He who blocks it  - Unblocks it."

 

 

That used to apply in the days when yacht toilets pumped direct into the sea, these days holding tanks are the norm hence it is difficult to identify the culprit.

[ProDave]

It opens out to 4 runs of 110mm perforated pipe. I would be very surpsised if the entire drainage field is blocked  I guess that is the worst case;l. Farmer won't be too happy if it needs digging up, he has just ploughed, but not yet seeded.

[ProDave]

1 minute ago, epsilonGreedy said:

 

That used to apply in the days when yacht toilets pumped direct into the sea, these days holding tanks are the norm hence it is difficult to identify the culprit.

I sail on old boats that do things the "old way"

[scottishjohn]

2 minutes ago, ProDave said:

It opens out to 4 runs of 110mm perforated pipe. I would be very surpsised if the entire drainage field is blocked  I guess that is the worst case;l. Farmer won't be too happy if it needs digging up, he has just ploughed, but not yet seeded.

so maybe the most probable is it blocked in the small dia feeder pipe--if it is a blockage

Edited February 15, 2019 by scottishjohn

[ProDave]

23 minutes ago, scottishjohn said:

so maybe the most probable is it blocked in the small dia feeder pipe--if it is a blockage

It has to be a blockage. The pump pumps at the bottom but there is no flow. 

 

I will let you know what tomorrows excavations find.

[Ed Davies]

53 minutes ago, ProDave said:

he has just ploughed

 

That's not a clue, is it? As in, could the ploughing have caused it to become blocked at the far end of the 50 mm pipe.

[Jeremy Harris]

How deep is the pipe buried Dave?  Just a thought, but you've had some sustained cold weather up there, haven't you, days on end down at around -10 or less?  Any chance that the pipe could be relatively shallow at any point on the run, so that it may have frozen up?

[ProDave]

I suspect the blockage might have been building up for a while. I replaced the pump a year ago, and it has failed at 1 year. They used to last between 5 and 7 years before that.  I doubt this years ploughing was the reason, then only did the perimiter run today and I am sure it had failed before then.

 

I also doubt it was freezing. We always get a few weeks of really cold weather. It it had frozen, I am sure it would have thawed in the last weeks mild weather. and if it had split as a result of ice (unlikely for mdpe) there should be a split and a leak and some wet ground somewhere.

 

[epsilonGreedy]

1 hour ago, Ed Davies said:

That's not a clue, is it? As in, could the ploughing have caused it to become blocked at the far end of the 50 mm pipe.

 

 

That is a good point. I used to watch the ploughing next to my old house in the heart of East Anglia's fenland farming agribusiness. A modern tractor will visually lift up a dome of earth for meters around the plough so the horizontal disturbance to the soil could radiate beyond the directly ploughed area.

[Onoff]

Could the previous ploughing have cut the pipe and then blocked it with a sod of earth? Hope not.

[epsilonGreedy]

2 hours ago, ProDave said:

I sail on old boats that do things the "old way"

 

 

Yup still legal and normal practice in British waters. The Mediterranean yacht charter market dictates the standard fit out of new European yachts hence holding tanks are becoming the norm. There are also regional differences, the tidal range in Scotland is nearly double that of say Yarmouth IOW so lots more tidal flushing action up north.

[PeterW]

Unless he was subsoiling its unlikely a plough has hit it as most farmers have gone min-till these days and even when ploughing you're only in 8-12" at most. 

[Mr Punter]

Drain rods without fittings (you may need to borrow some extra sets) will let you establish where the blockage is.

[ProDave]

Okay results of the morning.

 

located the mdpe pipe in the field margin before it enters the actual soakaway.  Drilled a 4mm hole, turned the pump on and we only get the slightest dribble of water from that hole.

 

Located the pipe closer to the pumping chamber, drilled a hole and when the pump is on we get a good fountain squirting 6ft in the air.

 

So the blockage is somewhere in between.  Having lunch now then back to digging more holes.