leaking sprinkler zone...what do i do?

i noticed one of the sprinkler heads leaking when the water is off. the system still waters fine but that head seeps when everything is off. i thought i just needed to replace the one head so i removed and capped it. when i capped it the other two heads in the zone started seeping(more of a fast leak...spray up a little). the leak seems to come and go...if i turn if off and on a few times it may stop leaking but only start up again next time its used or what not. the sprinkler system was self-installed by the previous owner and i don't know where anything is under the ground. what could it be?
thx
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the valve feeding the zone is leaking....
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why would it leak some of the time and stop at others? i just went outside and turned the zone on and now there is no leaking.
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Most likely because there is some dirt getting into it. Typical sprinkler valves have a very large and pretty soft rubber seal. Dirt (typically sand or grit that comes in with the water) can get stuck on that seal. We have experienced this problem frequently at home.
Here is a set of possible cures (in order of easy to hard): 0. Turn the valve on again, off again. If you get lucky, the dirt is swept out. If you get unlucky, more dirt gets stuck on it. 1. Take the valve apart. On most valves that can be done by unscrewing a ring of screws that hold the top on. Then clean the rubber seal, maybe with a little brush. Look for grit stuck in the rubber. 2. If you regularly find dirt, then flush out all the lines with clean water. Open all the sprinkler heads completely, and flush as much water as you can through it. If you can disconnect the valve and lines completely, it is an even better idea to backflush all the lines leading to the valve (flush them with the water going the opposite direction). 3. The rubber seal is supposed to be soft, not cracked or hard. If it isn't soft, replace the rubber seal. For most consumer-grade valves, you can't get rebuild kits, so the easiest thing to do is to buy another valve of the same exact model, and only use the new seal (save the rest for future cannibalistic repair). 4. If nothing has helped yet, then the water source is continueing to bring dirt into the system. To prevent recurrence, install a strainer or filter in the water, upstream of the valve. But if you have dirt or grit in the water, you'll have to regularly clean the strainer or filter, otherwise it will plug up.
Note: When I say "dirt", I mean particulates that are large enough to block the valve open. This has little to do with the color of the water (it might be completely clear, with some sand being dragged with it). And it has little to do with the question whether the water is sanitary and safe to drink.
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SQLit wrote:

Could it be the "leaky" sprinklers are at the bottom of a slope and only run on from remaining pressure when the system is shut off?
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sounds like unless the valve is bad, you are seeing the remaining water in the line leak out the sprinkler head. Run the sprinklers, shut them off and watch the leak. If it stops after a while, that's probably what's happening. Cheers, cc

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4ax.com:

The valve for that zone is not completely closing when it is turned off. You have to find the valve and rebuild it (if you can get the parts) or replace it. Either way, without knowing where the valve is, you're in for a lot of digging.
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