White grout should be sealed after installation to preserve the look. Cleaning is much easier if it's sealed. Elbow grease is the best option. When it's as clean asit can get, seal it.
Ron

After the elbow grease Ron suggests, use hydrogen peroxide to further whiten the grout. Lay paper towels over the grout, pour the peroxide, let sit for as long as you can. Give stubborn spots an additional treatment. After you are satisfied, let it dry and then by all means, use a grout sealer as Ron suggests to prevent future problems.

Tile suppliers sell heavy duty grout cleaners that have the proper pH so the grout isn't harmed/weakened. About $6-8 a quart, I think. Gloves and eye protection recommended - use as directed.

"Tile suppliers sell heavy duty grout cleaners that have the proper pH so the grout isn't harmed/weakened. About $6-8 a quart, I think. Gloves and eye protection recommended - use as directed."

Anything so strong as to require gloves and eye protection IS attacking the grout.
Acids are normally used here.

Peroxide or bleach are not as hard on the grout as acids.

Bases (like lye) will not do much.

thanks for all the graet advice. I will attack it with the aforementioned tactics and products.. anyone have specific success with peroxide versus a commercially available product?
thanks again,
dave

"Anything so strong as to require gloves and eye protection IS attacking the grout.
Acids are normally used here."

The product to which I was referring:
Aqua Mix Heavy-Duty Tile & Grout Cleaner
According to the jug, it contains sodium hydroxide and is a high ALKALINE cleaner-degreaser. Avoid all skin contact, do not kneel in product, wear gloves and eye protection, etc. etc.

This was recommended by the folks at my local DALtile.

"According to the jug, it contains sodium hydroxide and is a high ALKALINE cleaner-degreaser."

The least effective way to even try cleaning cement type products like grout.

Try some TSP (tri sodium phosphate) and hot water.

For what it's worth:

http://www.mapei.us/pdf/TechBulletins/GroutCleaning_TB_EA.pdf

Peroxide is the same product that is in the tooth whitening products. It's also very inexpensive and less caustic than other products. Bleach is quite effective but I suggest starting with the peroxide since it most times does a good job. Before using any of the more expensive specialized products, peroxide or bleach have been very effective on coffee stains that discolors white grout on tiled kitchen counters as well as white shower tile grout and most homes already have them there. You may as well work your way to the product that does the job to your satisfaction since the issue will eventually resurface sometime down the road. I think you'll find the least expensive approach the way to go. Test a small area and see what results you get. pour some on, press a paper towel onto it, add a bit more and let it sit for as long as the towel remains wet. If you're in a big hurry to get it done fast, you'll have to use the more aggressive approaches but, if you can wait a few hours, they are not needed. Treat the spot, go to work and when you get home, you may be delighted with the results.

Well, I came up with an amazing solution and indeed it was completely by chance: a small area of grout looked whitened, especially next to all the stained, yellow-brown areas so I hunted around the bathroom for what might have caused the fix and there it was in front of me: Mrs. Meyers Clean Day Products Surface Scrub, an all natural product made right here in Minneapolis, MN!
Looking at the label, I think it's probably the oxygen bleach which does the hard work and it does that work amazingly fast and well. I have not taken on the whole bathroom floor yet, but now that I have a good solution, I will soon. Below is a link to this product for anyone interested in a good grout whitening; and when I finish, I will be sure to seal the grout this time!
thanks again and happy DIYing, dave

Here is a link that might be useful: Mrs Meyers Surface Scrub

Having the same problem in my bath, I have decided that it was just a mistake to have white grout and asap I plan to go over it with something darker. I mean look at all the suggestions here - all very labor intensive to keep up every week or even more often. I have better things to do, don't you?

Meanwhile, I have had some success with my steam mop. It only uses water, so I guess it can't be too hard on the grout.

Having the same problem in my bath, I have decided that it was just a mistake to have white grout and asap I plan to go over it with something darker. I mean look at all the suggestions here - all very labor intensive to keep up every week or even more often. I have better things to do, don't you?

Meanwhile, I have had some success with my steam mop. It only uses water, so I guess it can't be too hard on the grout.

We bought a 1950's ranch with original pink tile in the bathroom. It looked dirty amd gray in the grout lines. I bought white ceiling paint, applied it to the entire floor, wiped off the excess, letting the white paint settle and dry in the cracks. It looked fabulous and lasted about 15 years. The whiteness was nearly blinding! We re-did the bathroom in 2006 with all new tile and new grout, with sealant applied, but it's now looking grubby. I have some extra ceiling paint. . .

I have had great results by using oxygen bleach. It is a very good cleaner brightener and is biodegradable. Oxyclean works pretty good but it is not as full strength oxygen bleach as some other products. I have used a product called 'stainsolver' which does a great job. But, it is not cheap. www.stainsolver.com

Someone in the bathroom forum used BarKeepers Friend on an old bathroom floor and it worked really good on the grout. I have not tried it yet. I sealed my floor but the grout still gets yucky.

We just had a grout cleaning company come in, and the guy said to never use vinegar or bleach on grout, as it will weaken the grout. He said to avoid even the oxyclean, which was recommended on another thread. This was a company that got high ratings on Angie's List. We are going to pay to have the tile floor steam cleaned and sealed. Fingers crossed that it works!