pex in old pipe?

Water supply pipe to secondary building has a leak - somewhere. Originally installed 60+ years ago, it is black plastic water supply pipe. Comprised of various sizes - whatever was available in the barn at the time, it is now covered in most places and overgrown with large roots and brush piles that are rotting in place. This is a seasonal site and the water pipes get drained, but not blown out. And they run generally downhill, with several pockets that bend around stumps and rocks so they are not entirely flat.  We do freeze during the winter and piping was laid on the bedrock in some places about 6 inches below surface level.

Instead of trying to dig all that up (I think the minimum pipe size is 1 1/4" and some 2 1/2"), someone suggested I try to push a length of 1/2" PEX pipe through, effectively turning the old black plastic into a conduit. From source to sink is about 130 feet. Anyone tried this method? Any thoughts of alternatives?

Thanks,
Randy

If it was a straight run with a continuous pipe, it might be viable. I think simple water-certified poly would be cheaper and simpler than PEX.

But if it has bends and joints, I forsee endless opportunities to run into problems. The joints will have a barbed connector, which is a pretty effective barrier.

Can you find the joints? That's the most likely failure point anyway. Corroded clamps after 60 years.

I wonder if you can rent a long sewer snake and see if you can get that through? If so, you might have a chance by pulling pipe through, with some sort of bullet shaped connector to slide past obstacles.

Personally, if the existing pipe can't be repaired, I think laying a new pipe would be a lot less hassle. And the result would be reliable. My 2c.

If you can find a ball that is somewhat larger than the pipe you want to put through, you can put it into the old pipe at one end and connect a vacuum cleaner at the other. If it makes it through you can attach a string to the ball and repeat to pull the string though. Connect a stronger rope and pull that through. Then you can use that to pull the new pipe through.

I'd put the string on in the first instance if I wanted to retrieve the ball when it hit an obstruction. Otherwise, you'll have rendered the line inoperable and changed your replacement schedule.

Either way, I think Douglas' advice is spot on. A line cobbled together from whatever was laying around is likely to be a dog's breakfast of couplers and reducers, and each one of those is a potential deal breaker if you want to push a line through the inside. You could maybe disassemble it and use the old lines as sleeves (minus the couplings) if you want the added protection of a conduit.

sounds to me like that pex idea might just work. but I would use 3/4 or 1" just in case you might want more flow out there for something. pex is not very expensive compared to other types of water pipe. get a roll and try pushing it through, you won't know till you try. but I try to be a glass half full kind of guy. if it won't go through you might only have to dig shorter trench from where it got jammed up if it even gets jammed up.

I come from the school of;
Do it right eventually!  
Its damaged and not working, after 60 years there should be some cash to do it properly now, no joins, just a clean straight run that will work forever.

Hi Randy,
It sounds like this is not in an area that is mowed or really has traffic? Could you just lay out some more black poly pipe on top the ground? If you are going to drain it before winter, then the only reasons to bury it are to avoid tripping/hitting it or for aesthetics. Unrolling it for the season and then rolling it back up and putting it in a covered place might not be a bad thing.

1/2 inch pex is not flexible enough to go around any 90 degree bends, but you might pull this off if there are only gentle bends. This would be easier on a hot day when your roll of pex would be more pliable.

An alternative (I have done for a similar situation) is to take a reciprocating saw with a long blade and cut into the ground at a 45 degree angle. Then I ran the pex along the cut and stuffed it in. This got it below the sod so there would be no fear of mowing over it. Not frost proof by any means, but I blow it out at the end of the season.  

John C Daley wrote:I come from the school of;
Do it right eventually!  
Its damaged and not working, after 60 years there should be some cash to do it properly now, no joins, just a clean straight run that will work forever.

This is something I need to remind myself. Take the extra time an do it right. A cob job is just a ticking timebomb.

Matt Todd wrote:An alternative (I have done for a similar situation) is to take a reciprocating saw with a long blade and cut into the ground at a 45 degree angle. Then I ran the pex along the cut and stuffed it in. This got it below the sod so there would be no fear of mowing over it. Not frost proof by any means, but I blow it out at the end of the season.  

Good idea! I keep junk recip blades for exactly this kind of thing.

I have buried black poly pipe underground for several hundred feet by making a slit in the ground with a shovel. Turn up a series of divots to lay over ("hinged" on the other side) so that a length of trench is exposed, place the pipe, and flip the sod back over to cover it. This gets the pipe safe from mowers and tractor wheels.
The reciprocating saw idea could work too. One might be better than the other depending on the character of your land and the availability of electricity.


My experience with feeding a remote sink with 1/2" black poly is that there is plenty of flow for a commercial sink even after 200+ feet. The pipe is fed from a hose bib on my house, and goes through some 1/2" copper pipe before that. So if you only need to supply one fixture at a time, you don't need big pipe.

Sounds as if you'd be able to give 1/2" PEX a go and have a decent chance of it just working. Chances go down each step up in PEX size you go, so if you wanted the bigger pipe, you might have to do some digging. MAKE A NOTE of the markings on the replacement pipe, they usually have foot markings (or two-foot markings) which might be a big number in the thousands, but sequential down the pipe... this way if you hit an obstruction, with some simple math, you can measure out above ground to know where to dig!

I agree with Phil, that whatever you pull through ought to be able to be pulled back out if you encounter an obstruction. (not just loose like the ball idea to see if it will pass)
An obstruction could be any number of things:
a flattened/crushed pipe considering how shallow it is.
tree roots grown into a break in the pipe.
a broken fitting joining the pipes
something piercing the pipe/a deformation left behind from the piercing thing.
a rusted steel/iron fitting, clogged by rust, maybe also the source of the leak.

I'd do some exploratory excavation, to maybe discover what pipe sizes and fittings are *where* and for how long... pick some easy spots (not tree roots) to uncover what's going on down there. Split the distance up and if what you find matches the end in the nearest building (pipe size, type, markings if any) then go halfway to your nearest hole that is different... until you find the joint.
If for instance, the 1-1/4" pipe made up only the final 25' and the rest was 2-1/2", you might be willing to dig that 25' out in order to use a larger replacement pipe. Or you might find the leak is a broken fitting joining the pipes, and be able to just replace that and be done. Heck, 60 years could be a rotted hose clamp causing the leak, that would be easy to fix.

Another thought, you know there is a leak... presumably because you have a pump that keeps running periodically unless this line is isolated? Can you notice any wet areas in the route it travels? squishy soil? a spot with greener vegetation downslope of the route?

The area where the pipe runs is both the primary walking path and the occasional tractor path - sometimes with really heavy loads (think one yard boulders).

Dad ran the original pipe through the woods off to one side of the path (7 to 10 feet wide) from the house to the boathouse ( about 120 feet). It supplies one small sink that has infrequent use, and a solar heated water tank that only gets used after swimming to rinse off the salt water.  But oh, so welcome come the 60 degree water temp we are heading for!

The terrain is not forgiving - roots, rocks and a couple areas of large riprap for a retaining wall.  The only place I could put a new pipe is right down the middle of the path.  And that has exposed spots of granite bedrock, so it would become a tripping hazard.

I'd love to do it right and anew, but the work involved is far more than the reward I get for the effort. And since we are only ten feet or so from the ocean, it could open me up to a ton of possible permitting issues.

I don't recall any hard bends in the existing pipe, so I think I'll give the "suck a ball on a string through" a try and hope for the best.

And thanks to all for their input.  I'll let you know what happens.

We had a run of 1 1/4" black poly from the house to the cistern running about 70 feet.  Used as a conduit for 1" cross linked poly when we put the city water in instead because the poly line wasn't heavy enough for the city water pressure as it had only been suction from the cistern.  Worked fine.  Really close fit and took lubrication to pull it thru.  Big thing is it saved digging near the house.  Since the sidewalk was right over where the water line came in it saved more work too.  I would suggest bigger than 1/2" PEX if possible.  We put a rag on a rope and blew the rope thru with compressed air.  Then we built a pointed end that was screwed to the end of the inner pipe to hang onto it and pull it thru.  If they are doing bigger distances they blow the rope thru, pull a steel cable thru so they can pull harder.