I am installing a dehumidifier in my basement. I want the hose( typical garden hose) to drain directly out so that I don't have to empty the tank all the time. The nearest drain line is a 4" PVC pipe. What do I need to tap into this pipe and install the hose into my drainage system? By the way, there is a clean out plug on this 4" PVC pipe near by that I can open and put the hose in, but how do I seal it to prevent leaks/smells? Is there a part I can buy to adapt for this installation? Thank you in advance.

I'm not a plumber but I can tell you that the way to prevent smells is to use a trap. If you do put in a new drain into the 4" pvc, you will need to have it vented. What else is on this 4" pvc above?

You may have a problem with the height too. You may have to raise the dehumidifier to make this work.

Check out a condensate pump. It's probably going to be cheaper than getting a plumber to put in a new drain and vent. You could then just drill a hole through the wall for it to drain outside or snake a line up through the floor to your laundry drain.

Hope it helps.

Pumping it outside is the green way to handle it too.

Basically the condensate (usually from an AC unit) gravity fills a small sump on the pump and when it gets full enough the pump discharges it outside. Typical heights it will pump is about 10'.

Everything else in the house is above this 4" pipe. It is right before it discharges to the main sewer line. I realize that the dehumidifier must be higher and it is 2 ft above the drain line. I know there is something that I can do to adapt this pipe or the clean out attached to it to accept this hose. I just haven't found it yet. Will wait for more suggestions. Thanks to all for your help.

Kiss nail it! A AC comdensate pump's, (see image) the way to go. Hartell make a very good selection. Check them out at ; Hartell > Products > Condensate Pumps > KT-15 Pump (http://www.hartell.com/corp/details/0,,CLI1_DIV32_ETI3740,00.html)
I have a KT -15 installed on my AC unit myself. Works great and you can run the hose outside to water the plants. A win-win situation. Good luck, Tom

Being cheap, I'd remove the clean out plug, install a 4" threaded male adapter, then a street 90. Bush that down to 1/2", build a trap out of 1/2" PVC (of get one of those preformed traps used for a/c drain lines). I would then install hose bib so I would have a hose thread to attach the hose. Get a male to female hose adapter or use a washing machine hose so that you have two female ends.

I would not bother venting this line because the dehumidifier will never fill up the 4" pipe.

Make sure that you have enough swing room to remove this contraption in case you need to snake the drain.