You should take that down to bare wood and pH balance especially if you are going to use a clear (which is an "iffy" proposition)

I would not even consider a water borne sealer. Oil Based for exterior projects. This month's newletter on my website explains about sealers. If you have any more questions, feel free to ask.

I think that Behr waterproofing "wood toned" finish may have been used on it previously, but most is gone. (we have a can of that in garage, but not sure if it was used for front or back deck -- back deck is now painted with olympic brown stain).

When I say I'm considering a clear stain, I mean the darker colors.

SHould I use cabot clear stain or austrailian timber oil?

THe can says Behr
Wood sealer and finish
Pressure treated brown
Wood toned finish

Again, I'm not sure if this was used for the front porch.
The residual color left under our front mat is similar to the swatch on the behr website

OKay I know the product you mean by Cabot's. I think they call it Clear Solutions. It has a very light pigmentation to it and will need to be applyed yearly. It lets most of the grain show through. It's a good product I have used it a few times. It will not go over the Behr though so you have to be sure that all of the Behr is off using a good cleaner/stripper. I assume you are keping the risers white? That looks like either paint of solid stain and that will not come off.

If I use the restore-a-deck product....
1) will it remove the behr stain
2) what type of pressure washer would I need if I wanted to buy one?

The original color of our deck seems like it the swatch for the red toned deck on the behr website.
http://www.behr.com/behrx/act/view/products?catId=13&sc_name=Wood+Waterproofers&vis_tab=oil
click on see finish sample

I like this finish. Which Cabot product would be similar.

I noticed in your article that you do not recommend clear stain. Which Cabot product do you recommend?

1) Yes it will, but it will need to dwell longer. You would apply the cleaner heavily and keep it wet with the cleaner for 30-45 minutes. You would be able to tell if it's ready to come off by using a rubber spatula or tongue depresser and rubbing it along the surface. The emulsified oils will come right up.
NOTE: Look on your can of sealer. If you see the word "acrylic" a sodium percarbonate based cleaner will not work.
2) For a portable machine that will give you long life and make your job easier look for something in the 3 gpm range or higher with a gas engine. The little ones they advertise on QVC or the ones at Home Depot are not wiorth the agravation. They clean about as fast as a Water Pic. Click on the link below to see a machine that is value priced but still effective.

By clear stain, I mean a product that has no color tint to it whatsoever. It looks like baby oil in the can. The Cabot's Clear Solutions or Deckscapes Toners are products that provide a slight advantage over using a clear sealer. For consumer products that show a ton of wood grain I prefer Sikkens SRD penetrating oil.

Here is a link that might be useful: Pressure Washer

I think it has acrylate. What would I use then?

I was considering a $400 gas powered one from Costco...its about 2500/3000 psi. But do I need one with your product? I would prefer not to buy one.

The psi is unimportant. It's the gpm that counts for speed. With a product like Behr on there I recommend using one. You could also just use a brush to agitate stuborn spots and recoat area that do not come up the first time but this will add time to the project.

I stained my deck last summer, aftera long winter a lot has come off,when i went back to re-stain this year it did not cover the bare spots. I cleaned with the recommended cleaner 2 days ago, it rained hard for 2 days and today i am trying to complete and it's not covering. Do i need to clean again?