I'm using a round grey plastic (outlet type floor box) out side for a pool circuit as a pull box because the run is long. The plastic blank cover that that comes with the box.. is it ok to use that as a cap outdoors? No outlet will be there, just a junction box. Or is there a separate W/P cap I should use?

I would have a problem with the use of the materials you indicated you were using for this installation. They do make listed boxes for that application. Hopefully it's not for the pool light.

Ever think of using a handhole box?

They can come in real handy sometimes.

No its for a fountain. Its the same box they use in cement for floor boxes, so it is weathertite. I was just wondering about the plastic cap they give you. It looks to be weathertite too. Unless they make a different W/T cover, I have never seen one. If they do I will go back and change it.

The plastic cap they give you is to keep out concrete and debris when this box is used per its listing. It's not a finish or waterproof cover and the box isn't listed for the use you describe as they can only be finished with floor box covers.

Do they make a blank cover for that box?

Why would they make a blank weatherproof or water tight cover for a box the IS NOT LISTED FOR USE AS YOU HAVE DESCRIBED? I can only expect that you don't plan on having it inspected or you don't care. Change the box and get one with the proper cover.

Why would it not be waterproof, it is PVC just like the pipe going into it. If there is a special cover for it I will get it, or I will change the whole box out. I'll check with my supplier. Don't know of any other better weatherproof box.

Aldav,
As others have said, you NEED a handhole box for this application, a floor box is the wrong gadget for the job. Ask you supplier for a "Christy Box" and see what they have.

Check out their catalog: http://www.christyconcrete.com/elec_com_boxes.html

You probably want an N9 or FL8. Set it in a base of crushed rock so the bottom can drain, bring your pipe in the sides or bottom, and pour your finsihed concrete around the sides. Use waterproof wirenuts if you are splicing in this (though it's better if you don't), and provide bushings on all your conduit.

Quazite makes something similar. You can get boxes from 6"x8" all the way up to "gigantic".
They're at www.quazite.com

This is just a couple circuits for residential.
The same PVC we use underground is connected to it.

Is this carlon round box listed for outdoor use? I have only used them indoors before. If it is listed for wp outdoors, then how about using the receptacle cover and a receptacle that is not connected to any wiring. Label as unused.

This box has a solid bottom, the thing will fill up with water the first time it rains or the sprinklers come on. Also, you don't know if the lid is UV resistant or strong enough for walkover use, what's to say it won't get brittle and crack after 2 months in the sun? Then somebody steps into it and you have exposed wires and a broken ankle.

As I understand it, there are two code compliant options for a below grade situation:
-A handhole box
-A bronze "deck box" with listed potting compound installed*

*this may not even be legal, as I know there are restrictions if it's an Art 680 installation

I'll check on it, I'm sure the box is w/p it has to be its the same as PVC pipe, but I'll check on the cover.

there are not safety standards for floor boxes intended for outside locations. The UL514 standard (water exclusion covers) is intended for concrete floors and do not mention about out or inside locations, however since the UL water exclusion test is only to prevent water from enter into the box for only 2 minutes, placing a floor box in outside locations is not recommended.

"the box is w/p it has to be its the same as PVC pipe "

This is debatable.

No matter how carefully it is prepped, PVC conduit buried underground usually leaks, and depending on the pitch of the pipe, you will end up with a box full of water.

Quazite (or Christy) is the proper way to go. About $100.00 for your application.

How have I missed this thread for so long?

There is no such thing as 'waterproof' in electric work. I don't care what the material is,or how the connections are made.

This is because the wires themselves are not waterproof ... moisture can wick through the strands. This is because the pipes are all 'open' where they enter boxes. Moisture will condense, then accumulate in the low spots. As a consequence, even in the desert, buried pipe is considered a 'wet' location.

The temporary plastic cover that comes with floor boxes has not the strength, or sunlight resistance, or gasket needed to make it an acceptable permanent cover.

So, you need to take a different approach. Rather than trap water in, you need to make sure it drains. Here's how it's done:
A "handhole" is a fiberglass tube, with a cover for the top only. Approximately the size of a 5 gallon bucket, it has a rather substantial flange for anchoring it in place, in the ground.
Typically, you will dig a little deeper than the handhole, and put a layer of gravel down. Not only will this let water drain, it will help keep down the amount of roots and bugs in the thing.
Your pipes do not connect to the handhole; they will either come in the side, or (better) come up into the bottom. You will leave plenty of wire to work with; 'loose wire' 18" long isn't unusual.

For connections, I use ordinary wire nuts, then dip them in 'scotch-kote.' I take care to place them in the handhole so that they drain.

The handholes sold for electrical use are somewhat sturdier than the ones used for lawn sprinkler valves. The covers are available with a variety of markings. While the $50 price may seem a lot, the installed product will survive being driven over by the gardener, and will not shift in the ground.

Attempts to use other products - floor boxes, bell boxes, etc - always result in any metal corroding, the box (no matter how gasketed) filling with mud, roots, etc, ... and the pipe breaking where it connects to the box.

Another problem with using these smaller boxes is that your pipes are never deep enough. Code issues aside, shallow pipes get broke - usually when the gardener looks for a leak in the sprinkler system. You want your pipes at least a shovel-blade deep in the ground.

Finally, 1/2 PVC was created by the devil, to make your pulls hell. You can forget ever being able to re-pull wires. ALWAYS go up a size or two.

George grazed this question but it needs to be asked directly. Is this feeding the underwater light? That certainly changes the answer about what is necessary.