Finding a blockage in a 50mm mdpe pipe ?

[joe90]

Seems odd you hear a good flow from the house end but don’t get a good flow at the top? Leak? Plough damaged pipe?.

[ProDave]

17 minutes ago, JSHarris said:

Is there any way you can do a crude test to see what sort of head the pump can deliver? 

 

Perhaps pointing a (restricted) pipe up vertically to see how high it will raise a fountain might give an indication of how well it performs with the outlet restricted?

Apart from the garden hose (reverse the fitting I made) I can't see an easy way.  The only other bit of pipe I have is a bit of 25mm mdpe, but I don't like the idea of piping grey septic tank effluent down it, I would rather keep it clean in case I want to use it for potable water.

[ProDave]

Just now, joe90 said:

Seems odd you hear a good flow from the house end but don’t get a good flow at the top? Leak? Plough damaged pipe?.

The point is I can't measure flow. My hole and "height of fountain" is a crude measure of pressure, but not flow.  Thinking about it more, if I did get a big fountain at the top that would be a sign of a blockage in the field, but I don't get high pressure there, so it must be flowing freely into the soakaway?

 

There won't be plough damage in our garden, and I am 100% certain the entire soakaway is well below plough level.

[scottishjohn]

27 minutes ago, JSHarris said:

Is there any way you can do a crude test to see what sort of head the pump can deliver? 

 

Perhaps pointing a (restricted) pipe up vertically to see how high it will raise a fountain might give an indication of how well it performs with the outlet restricted?

a length of hose tied to some ladders 

[Declan52]

If you reverse fit the hose then time how long it takes to fill a large bucket/drum. 

[ProDave]

Okay an update.  The Italian pump arrived today, the only difference for saving well over £100 by buying from Italy direct, was it came with a Schuko plug on the end.

 

The bad news is the pump runs but nothing pumps away and I still just get a dribble from the top "test hole"

 

Next plan, expose more of the pipe at the bottom pit so I can cut it, and then try rodding it from there.

 

Anyone know if you can get a 50mm mdpe slip coupling?

[Mr Punter]

You could use a band seal type like https://www.wolseley.co.uk/product/flex-seal-dc65-drain-coupling-50-65mm-pf91540-44/

[joe90]

17 minutes ago, ProDave said:

Next plan, expose more of the pipe at the bottom pit so I can cut it,

 

If you can cut it then you could see the amount of flow if any then make a judgement on where the blockage is, up or down.

[ProDave]

2 hours ago, Mr Punter said:

You could use a band seal type like https://www.wolseley.co.uk/product/flex-seal-dc65-drain-coupling-50-65mm-pf91540-44/

The joint I will have to make where I am cutting the pipe, will have to be able to withstand the full pump pressure of about 7 metres head, without bursting, I am not sure that can do it.

 

[ProDave]

2 hours ago, joe90 said:

 

If you can cut it then you could see the amount of flow if any then make a judgement on where the blockage is, up or down.

 

So far we have only found the pipe in 2 places, one just a few metres from the pump chamber, and one just a couple of metres from the soakaway where it goes into the field.  Attempts to find the pipe at intermediate points have just resulted in very deep trenches.

 

This highlights the importance of keeping photographs and notes.  I didn't do much of either when we installed this.  But I do recall the ground levels were quite different. From the pump chamber, the pipe crosses a culvert over the burn and in essence then goes up a hill to the field. But the reality is the original ground level went down before going up.  the ground later gout built up to use up surplus soil and level the garden.  This is why I think it is so deep, because it goes down then up.

 

Now thinking about it, that is not good.  without thinking about it or considering it, I created a "sump" and any sludge will naturally collect there and my theory is that is where it is blocked.

 

If rodding it won't clear it, then I will be fitting a new section of pipe from the known good point near the bottom, to the known good point at the edge of the field, but any such new pipe won't be as deep and definitely won't have a "sump" 

[epsilonGreedy]

2 hours ago, ProDave said:

Anyone know if you can get a 50mm mdpe slip coupling?

 

 

You can, £18 at Pipestock.

 

https://www.pipestock.com/plasson/mechanical-fittings/repair-slip-coupling

[Onoff]

4 minutes ago, epsilonGreedy said:

 

You can, £18 at Pipestock.

 

https://www.pipestock.com/plasson/mechanical-fittings/repair-slip-coupling

 

£8 delivery.

[ProDave]

I have just bought this pair https://www.ebay.co.uk/itm/254026764133

 

a slip and a normal for £10  I hope they are the right thing, just described as "50mm black poly"

[epsilonGreedy]

1 hour ago, ProDave said:

I have just bought this pair https://www.ebay.co.uk/itm/254026764133

 

a slip and a normal for £10  I hope they are the right thing, just described as "50mm black poly"

 

 

Have you tried my suggestion of applying some reverse pressure on the pipework from the far end of the system?

[ProDave]

13 minutes ago, epsilonGreedy said:

 

Have you tried my suggestion of applying some reverse pressure on the pipework from the far end of the system?

Very much more complicated. That would mean digging up a lot of the top bit to cut it, fit a 50mm mdpe to something a lot smaller adaptor.

[Declan52]

What about using a cobra to see if it is blocked and then you can mark it,  pull it out and lay it on the ground along its route to give the  x marks the spot. Some hire shops have them. 

http://www.dartsystems.co.uk/products/cable-installation-external-pipedart-compact-cobra-duct-rod-c-72_69_195/

[joe90]

4 hours ago, ProDave said:

I created a "sump" and any sludge will naturally collect there and my theory is that is where it is blocked.

 

That seems very likely considering what you have said so far, ain’t hindsight a wonderful thing?

[epsilonGreedy]

11 hours ago, ProDave said:

Very much more complicated. That would mean digging up a lot of the top bit to cut it, fit a 50mm mdpe to something a lot smaller adaptor.

 

 

How deep is the main 50mm pipe as it exits the pump chamber and at the other end before it branches into the field?

 

I am raising this again now that you have a theory as to why the accidental sump is the root of your problem. In your position I would install a branch at each end that terminates at ground level to facilitate annual purging with reverse pressure, if an initial trial unblocks the system.

[ProDave]

6 minutes ago, epsilonGreedy said:

 

How deep is the main 50mm pipe as it exits the pump chamber and at the other end before it branches into the field?

 

I am raising this again now that you have a theory as to why the accidental sump is the root of your problem. In your position I would install a branch at each end that terminates at ground level to facilitate annual purging with reverse pressure, if an initial trial unblocks the system.

 

Close to the pump chamber where it passes over a culvert it's only about half a metre down.  At the field margin just before entering the soakaway it's about 0.8 metre down.  In between it's anyone's guess as 3 trenches over 1 metre deep have failed to find it.  I might consider the idea of a tee and a "sample point" capped with a stop end, but better would be to engineer the equivalent of a rodding eye.

 

But if I do re lay it with a new pipe I will be avoiding making a sump.

[scottishjohn]

maybe lay a  tracer wire on top of it --so you find it next time  

[ProDave]

So another day and nothing definitive.

 

Yesterday my big fat 50mm mdpe pipe couplers arrived so I have just been and enlarged the hole near the bottom and cut the pipe.

 

I sent my drain rods up it snd they met no resistance.  I have 10 metres of rods which was not enough to reach the end, but it would have been well past "the sump" and half way up the hill to the highest point.

 

As a sanity check I tried turning the pump on with the pipe cut and got a good high flow fountain, so definitely know it's not the pump or the pipework up to that first inspection point.

 

I am now torn between buy some more drain rods so I can really rod the whole length from the bottom, or open up a big pit at the top and cut into the pipe there and rod it down.

[Onoff]

Could you attach the pump to the other end and try and shift anything in there "downhill".

[PeterW]

50m length of cheapo PEX is £30, attach to the pump and use as a poor mans drain jet or use the hose on the end. 

[ProDave]

1 hour ago, Onoff said:

Could you attach the pump to the other end and try and shift anything in there "downhill".

Not without some serious work and finding yet more large pipe fittings.

[ProDave]

1 hour ago, PeterW said:

50m length of cheapo PEX is £30, attach to the pump and use as a poor mans drain jet or use the hose on the end. 

Now that idea I DO like. I have some left over PEX from the UFH that I am sure is long enough and with the hose attached I will give it a go.