I live in a terrace house and my gutter keeps over flowing every time it rains heavily. I've found out that my gutter is a bigger size than both my neighbours' gutters on either side of me. Can I take my gutter out and fit the same size as my neighbours'? If so, will this solve my problem?
Your gutter is overflowing because either the gutter itself is clogged up with debris or the down spouts are clogged up.
Your larger sized gutter should be able to handle more rain than the smaller sized items installed on your neighbor's houses. So a smaller size would be even less able to cope with the problem than the size that you have.
I suggest that rather than fitting new gutters it would be more cost effective to unclog the existing gutters and make sure that water can flow properly along the gutters to and then down the spouts.
There is a slight possibility that some of your gutters may have been installed incorrectly such that they have a slope away from the down spouts. If this is the case then rain would gather and run toward the down slope end and then overflow because there is no where for it to go.
I agree that adding smaller gutters won't make the problem disappear, it will even make it worse. The bigger gutters collect more water, which makes them more effective during heavy storms. You should get up there and make sure the gutters are not filled with leafs, and clean them up if they are. Sometimes the clogging is inside the downpipes, so once you clean the gutters, you should test the system by pouring some water on the top and see if it finds its way down through the downspouts.
Another thing which should help you prevent such issues in the future is trimming the nearby trees regularly. This way the chances of leafs and small branches falling inside the gutters during fall will be smaller. The gutter pitch is also something you should make sure is well adjusted. The gutters should not be installed even, they should lean towards the downpipes a little. I wouldn't recommend adjusting the gutter pitch by yourself, because it's complicated and mistakes can be easily made. But if you still decide to do it, you should check the blog of this company - http://www.paulsguttercleaningsydney.com.au/ , they have lots of tips on how to clean gutters, repair them and take care of them in general. I think I noticed a post on how to adjust a gutter pitch somewhere in there. They even give precise measurements and how should everything be done.
I would also recommend getting gutter guards or gutter sponges, they will prevent this from happening in the future. You'll still have to check the gutters twice a year, but the debris inside will be a lot less.