How to get rid of water in underground sprinkler pipes and fix tee thread joint leaks with minimal digging

Some of the pop-up sprinkler in the lawn leaks.  It's not the sprinkler.  Must be the threaded joint in the tee down below or worse. It turns out that my ex-gardener used a metal nipple to joint the tee below to the sprinkler.  That means he repaired the bad thread by making it worse.  I don't know how many he did.  If the sprinklers are not near the concrete driveway, it's hardly noticeable.

It's never easy to replace a section of PVC pipe, not to mention an underground tee piece.  You need at least two bulky unions or worse, two extendable repair pipe sections.  The total cost is silly when a tee is some 20 cents.  For me the labour cost is infinite as I have to dig out enough soil for all those things to get in and under.

I searched the net for ideas and found only one video inspiring.  Of course it is in you-tube.  All credit to him.  What he did was drill the thread joint to enlarge it to become a slip joint.  And sand down a short pvc section to glue to it.  Then you can attach anything to the other end, use a shorter sprinkler or install a flexible swing joint.

After drilling the thread joint on the tee, I think it's easier to drill enough so you can screw in a pvc male section, or just a threaded nipple that you would normally use.  So it depends.  If the thread are very loose, it may be easier to turn it into a full slip joint.  My threads are all "screwed up" so I can't even screw in a nipple.  After drilling with a 3/4" wood hole drill, I can screw in a nipple and have a rather rigid joint.  The nipple doesn't wobble.  There seems to be some good thread left or the bad thread still holds the nipple in position.   If I use PVC glue to seal the thread it would be better than a slip joint.  The PVC glue weld both pieces together to form one single piece with the same thermal properties.

Now the only thing to do is to dry the tee and apply the glue.  It turns out to be impossible.  Closing the water supply, turning on the valves doesn't drain the pipes.  Taking off the entire sprinkler down the slope doesn't drain the pipes.  Blowing air into the pipe with my air bed pump will get rid of water for a moment until more water come back.  I searched the web for ideas and time and time again they use air compressor to force water out of the pipes and out of the other sprinklers.

I don't have an air compressor and it's silly to rent one for a simple job.  I have a hand pump that is ideal but it is for oil change.  I can still use it but then I will be polluting if I just pour the water down the drain.  Pond pumps will be ideal for 1/4" tubes but they don't have inlets.

You-tube have plenty of water pumps that use electric air pump as the driving force.  The problem is that you can't get an air tube down the tee bottom with enough space for an inlet/outlet tube.  Without that you can't lift water with air - the principle of air lift pumps.  I spent a few days in experiments on and off to realize that.

The other possibility is venturi water pump.  But water pumps using that principle are probably not using that principle.

Just when I'm ready to order a real water pump I remembered that I have this:

 

It's as good a pump as anything.  I repaired the broken tube with packing tape, and taped a 1/2" pvc pipe to the hose end.  I have the 1/2" to 1/4" tubing adaptor.  It takes less than a minute to suck out all the water, not even one bucket full.  I also have a wet vac which is easier to attach a pipe to it.  Silly me.  But then I have no idea why everybody use compress air to blow out.

All the time and effort works out.  I saved some money and delivery time.  I learned some science.  I don't need to spend money on tools I already have with superior performance.  The pay off will be coming when I have to check and repair god knows how many sprinklers.