# Water in PVC line under slab



## kswoodshop (Dec 30, 2018)

I am setting up the DC system in a newly constructed shop. I ran a 4" PVC line under the slab for the table saw and jointer in the middle of the floor. When I unhooked the hose to this line I discovered water in the hose, and in the under slab line along with some wet sawdust. Either it is condensation, which would explain it being in the hose or there is a leak in the pipe and water from recent rain got in. The weather has been colder recently, and the shop kept a consistent temp (60 F) with an HVAC system. Has anyone experienced condensation in these lines before? I have used the line all summer and haven't noticed a problem before. Any opinions?


Darren Ehrlich
Kansas Wood Shop
Galva Kansas


----------



## Steve Neul (Sep 2, 2011)

I would have guessed water is seeping into the pipe from ground water. If you used the thin wall pipe the joints don't glue together very well.


----------



## gmercer_48083 (Apr 9, 2016)

Darren, When new buildings are built, especially multi story buildings, city's require static pressure tests of the drain lines to guarantee no leakage. Basically they use a test plug at each end, with an air gauge in the line...add air pressure and the gauge will indicate if it leaks. Maybe you could rig something...it doesn't require much air pressure.


----------



## woodnthings (Jan 24, 2009)

*What is the construction?*

How is the line buried under the slab? Are there loose or glued fittings or connections? Is the slab "on grade" or are there footings around the perimeter? How can ground water enter it if the footings surround the slab would be my question. If the water table is so high that water is getting into the pipe, get ready for the slab to float away. :sad2: 



Condensation seems to be the only reasonable issue, but I could be wrong. If you can run a snake wire all the way from inlet to outlet, use some electrical wire and wrap a cloth around it so that you can drag it half way in from one end and then do the same from the other end. If it comes out soaking wet from either direction you have a puddle of water in the pipe. Now, you have to figure how how the water is getting in ......... :surprise2:


----------



## regesullivan (Jan 26, 2007)

When a duct runs in a slab on grade condensation is likely to be a problem. Chances are pretty good the air flowing through the duct to or from a DC is warmer than the walls of the pipe causing condensate to form. Picture the water on the surface of a cool glass of your favorite beverage then multiply that by a couple of hundred times or so depending on leanth and diameter of your duct.


----------

