Here's a PS to my review above. Some reviewers, here and on on Amazon, have thought that the o-ring isn't working because it appears to be leaking at the top. The maker is shy about giving an explanation, but I've figured it out.

Alongside the connection for the input hose, there is an upright spout with a little lid over the two holes on the sides beneath it. It is meant as an emergency overflow, if pressure builds up, but it lacks a valve, so it always spritzes water out. Some of this water (since it was moving upwards) sprays upwards and makes it look as though there's a leak at the top. Don't over-tighten the lid--you'll risk causing damage to the o-ring!

I've used one of these for a few years and am generally happy with it, thought I had the same problems with the ring seal on the cap and the cap leaking the chemically treated refill water into the tank. My other problem was the cost of the refills. I tired to use other "drop-in" toilet cleaner blocks in the system's container jar but it's too small for the other products to fit into it. (This is by design I am sure, so you can only use the Kaboom refill.)

I was wondering if a d.i.y. solution like this might work:

Take some sort of funnel with a long spout, like the kind that are used to pour oil into an automobile engine. Put the spout down the toilet's overflow tube. Hook up the refill hose that directs water down the overflow tube so that it directs water into the funnel. When the toilet is flushed, water will stream from the refill hose into the funnel which will direct it down the refill tube as normal. Now, given a large enough funnel, you can put any kind of "drop in" toilet cleaner block into the top of the funnel. As the water from the refill hose swishes over the block, the block dissolves and adds its cleaning chemicals to the refill water going down the tube and into the bowl. None of the chemicals get into the tank, which the major advantage of adding the chemicals to the refill stream. I am about to try this.

One potential problem I see is that as the block dissolves, it might shift and block the funnel, in which case all the treated water would overflow into the tank instead of going into the bowl. Also, when the most of the block has dissolved, a small part that remains might completely plug the funnel and then will drop down the funnel, down the tube, and into the bowl and down the drain with the next flush. Some sort of screen or rack at the bottom of the funnel should prevent these problems.

Another issue is that funnel should be positioned in such a way as to allow the overflow tube to let water from the tank go over the top of the tube and down into the bowl in cases where the toilet won't stop "running" and the water filling up the tank doesn't shut off. The overflow tube has to prevent the tank from overfilling and overflowing onto the floor.

Does anyone see any other problems or issues?

i just found that neverscrub is offering free shipping. check out www.neverscrub.com  this might help those with people unable to locate those refills

This is an addition to my earlier comments. I have found the spa tablets work better than the brand name refill. So save some money and get better results. Can't beat that.

I've got two of the original design and it takes a little effort to keep them going. I'm too cheap to buy the new style. The o ring on one of them failed, but I got a new one from a local plumber. The teflon tape on the threads is an excellent idea as are the spa tablets, I love to save some money. It's still a good idea, just a poor initial design.

I did purchase 2 of these. One fit in the old toilet but is useless in the new one. It just plain does not fit on the fixture. I threw away my receipt and am very unhappy with my purchase. I would not purchase this again because it has only a 50% satisfaction rate at my house.

and it is impossible to read your security

Thanks, Laral, for the tips. I will give the Teflon tape a try. Here is an update on my dealing with the company:

Recap: I called the Kaboom folks (Dwight something-or-other--don't have the company name in front of me), and they started out by saying that yes, there was a flaw in the design that I had bought from them, and that I needed to buy their new and improved design. I countered that it didn't seem fair that I just bought two if these, with a flawed design, and they wanted me to shell out for more to resolve their flaw. So in the end, the service rep said that he would send me a coupon for replacements. The coupon (singular) did arrive, and it covered the full price of only one replacement. The replacement does seem to be much more simple, and the cap seems to turn better. We'll see how it does after with a refill.

But I like the idea of the Teflon tape. Since they didn't send me a coupon to replace the other one, I'll give that a try.

I did notice that recently, the refill packets include a coupon for $2 off. So after buying one, I went back and got another with the coupon. As you point out, the refills at Walmart are about $3-4 each, so I just got a refill for $1.43 (I don't recall if that was before or after our 8.3% tax).

I thought often about the fact that the chemical seemed to be pretty basic. I kick myself that I didn't consider the spa or pool chemical approach! I'm anxious to head to Walmart and pick some up. Good thinking!

Seems like a good opportunity for someone to come up with good, solid, simple design that directs the user to buy the spa tablets. Maybe the company that makes the spa tablets should design and market their own toilet tank bases bowl cleaner ;)

Thanks again, Laral, for the great ideas!

Jeff, there is a technique to removing and replacing the cover. Leaving the unit in place, put your four fingers behind the tank directly in back of the unit and your thumb directly on the body of the unit below the cap. Grip everything tightly, pushing the unit against the inside of the tank with your thumb, and turn the cap with the thumb and first two fingers of the other hand. It should come off quite easily. Reverse the process when replacing the cap. Screw it down tightly so it won't leak. Make sure not to cross-thread it. I put some Teflon plumbing tape on the threads to make everything go smoother and to help the seal. I have no problem removing/replacing the cap and no leaks.

A word on refills. Refills for this are inordinately expensive. Mine only last about a month with just nominal use by one person. They are like $6 each plus about as much for shipping online. Walmart has them for around $3 which is a lot cheaper. But if you really want to save on refills, you can get a 1.65 lb. bottle of Spa Brominating Tablets at Walmart in the pool section for around $13. Four of the tablets fit vertically side-by-side in the cartridge. Four tablets weigh 1.65 oz., the net weight of the refill cartridges. Coincidence? I don't think so. That makes 16 refills for a cost of $.81 each. Since the tablets are whole, you don't get the overwhelming bromine/chlorine odor you get with the normal refills which are filled with a ground up version of the tablets. But you can still smell the chlorine/bromine odor that tells you it is doing its job. The tablets last twice as long as the refills for me as well. I wouldn't recommend pool chlorine tablets since they are stronger. The spa tablets are made for confined quarters and so are just strong enough.

"The agent is a deodorized form of bleach..."

I can't stand the smell. I'd really hate to smell it before it was "deodorized."

We'd rather scrub toilets than inhale the fumes.

I installed two of these in our house, based on the review here. After maybe two or three cartridge changes, I have found it near impossible to remove the cap to replace the cartridge (which, by the way, has been redesigned, apparently, to not be a cartridge with concentrated chlorine, but instead is a packet of two large clorine tablets). But worse, the cap doesn't want to go on all the way, and is very difficult to get to seal.

So the high concentration chlorine ends up leaking into the tank, which is contrary to one of the stated benefits of the Kaboom NeverScrub system. I contacted the company today, and they confirmed that the design of the system that we bought not long ago, has been changed, and I was told to go buy two more of them.

I balked at the having to buy it again, thinking that they should make good on these. I told him that we had just gotten finished buying a years worth of refills for two bathrooms, and returned them after running into this problem, and will buy new refills when we see how the company is going to handle the remedying of this issue.

The representative quickly said that he would send out a coupon. I will post an update here when it is either resolved, or not.

The cap is a problem with these for me too.