I recently heard about some folks having good luck using Thompson's water seal brushing or rolling on tents, boots, clothing, etc. Anyone here know if it holds water as to any first hand experience?
My three man (nylon)tent started getting some water coming in after the last week end scout trip in the rain and after 13 years, I put it through the wash (I know thats typically not done but it was time)so I will water proof this tent to see how much more life I will get out of it. It will be an experiment of sorts so there lies the question about what products? I haven't heard of great reviews on products like nikwax and fabsil so any others?
Thanks.

No personal experience with Thompson's.
Thompson's makes a sealant specifically for cloth and leather; is that what you're referring to? The website says it allows the fabric to breath, so I'd think it's got to just be a DWR coating like Mcnett, Revivex, etc. I've generally had good results with Nikwax products.
How was your tent leaking? Bleeding through the fabric, seams, etc.? If it's silnylon or PU coated nylon and its wetting out the fabric to the point of leakage, a fresh coat of DWR might be a very short term (or not at all) fix.

Thompson's works great on cotton canvas wall tents but I've never tried it on synthetics.

I've been wondering about this topic too. I have an ALICE pack and want to make it waterproof. REI sells a polyurethane coating to freshen up the coating on a tent. I was wondering if I could use it on untreated nylon of the ALICE. I was also thinking of spraying scotchguard on the outside. Perhaps not a goretex lined pack, but something.

I had a friend who water proofed a hat with Thompson's. Worked great, but.....the hat was stiff as a board and eventually cracked.

Thompson's will not work well on nylon and may destroy what's left of the existing coating. In the future, if you have to wash a coated nylon tent, handwash with mild dishwashing detergent, rinse and air dry. Use a mild bleach mixture for any mildew. Stop mildew early as it will destroy the waterproof coating and give you a bad case of tent leprosy.
Since your tent is leaking and was machine washed, it is likely totaled. If it is just the fly that's bad, you can sometimes call the mfg and buy just the fly if they still make that model or have pieces and parts laying around.
A spray on durable water repellent will help with problem spots but is no cure for a worn out coating.

Junglecarbine,As for the Alice pack, don't use the polyurethane repair coat. You will not like the results. Scotchguard or nikwax won't goober up the nylon fabric but will work better than nothing. The best solution is a waterproof stuff sack that goes in the bag. You don't have to use the old heavy military rubberized bags, use one large and three small silnylon stuffbags for the body and pockets respectively. Your stuff will stay dry, the bags weigh next to nothing and your Alice pack won't look all boogered up. Lightweight, waterproof coated nylon sacks are cheaper and work about as well as the silnylon bags. For my Alice pockets, I usually just use one ziploc freezer bags.

Quite a few years ago, I bought a 3 man tent. It was well past the warranty period before it saw any rain and I discovered that the floor wasn't coated. Can you say 'sponge'? I heavily sprayed the floor with Thompsons and it's still turning water 10 years later. I'm hoping the smell will eventually disappear. It's, shall we say, odoriferous.

Was this on a nylon tent and was the Thompson's oil or water based? Thanks.

It was nylon but I don't remember if the Thompsons was water based or not. It's been a long time. I just remember that I bought a 1 gal can.