valve
I replaced my water heater's cold water shut-off gate valve with a ball valve…because the gate valve didn't close all the way and was dripping water while I was working (installing a sediment filter.)
I'm assuming that, since ball valves are superior to gate valves, pretty much every plumber would agree that doing this was a good thing, but if there are any professional plumbers present, I'm curious to know what your thoughts are.
You need to find the main shut off valve in the road, side walk or somewhere on or near your property. They are usually placed in mini manholes with easy access:
But if you're unlucky you will need to get some building plans and try to find where on the plans the supply pipe runs and find the valve at the connection point to the main supply. In most cases it will be near the connection point of the main supply:
but if its not, or if you struggle to close it call your council to help you. You don't want to break that!
It is easy to snap these valves- if its rusted badly apply (known as WD-40, LN-40, HT-40) spray oil based rust release (spray leave an hour try again.. repeat a few times), TAP the valve with a hammer (!TAP!, do not whack it, to help release the valve. Also, usually opening the valve slightly helps to release it then try to close it.
I think what is leaking is the drain. Does it look like the object sticking out to the side in the below picture? If so, this is used to drain water from the house side of the supply when the valve is off.
It sounds like you over tightened it in the first place which started the leaking. If you've broken only the cap, you might be able to find a replacement. If the stem and threads are damaged, long-term you will need to replace the entire valve. As a short-term fix, you just need to block it some how. Marine epoxy is handy for emergency plumbing repairs.
Best Answer
I'm not a professional plumber (though I did work on water treatment systems for several years), but in my opinion what you did is fine.
Gate and globe (stop) valves are prone to corrosion and generally wear out over time. Ball valves are much more durable and reliable. I've seen many, many old stop valves that are leaking or don't shut off properly, or more often, leak as soon as you open/close them after they've not been touched for years. I can't say the same for ball valves - I've seen many that were installed for many years and still worked. I can even think of a couple where the outside looked totally corroded, and though it took a lot of force to turn (and sometimes a replacement handle), they still reliably shut without leaking.
On top of the reliability, the fact they use a 1/4 turn (instead of several full turns) and a quick glance tells you whether it's open or closed, ball valves are just vastly superior to gate and globe valves for almost all residential applications. Worth the extra dollar or so they cost.
The only thing they are not as good for is applications where you want to limit/control the flow rate (such as an outside tap or sample port). They can still do that, but are harder to finely adjust, and especially when one hasn't been opened for a long time and is a bit stiff, tend to suddenly give and open to full blast (I've been sprayed while trying to take water samples many times).