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View Full Version : Dam wall retrofit for a tap?



gbell
09-09-2009, 11:11 PM
Hi Everyone,

I have a basic dam in a gully - wall's only about 500mm high above spillway, dam itself is only about 1.5m deep, but will be dug out soon.

Is it feasible to cut a trench in the dam wall to run a pipe, then rebuild the wall?

gardenlen
10-09-2009, 05:10 AM
g'day,

for me if you have a functional wall i'd be suggesting leave well enough alone, and running an out feed like i think you mean can have its issues that being if you don't get a good seal around the pipe slow water movement through the wall could compromise the wall, we looked into as a possibility on a property we were looking at and decided then if we bought which we didn't buy, not to do it, can't rememebr now but we found info' online on how to do but then you have to rely on the bloke building the wall to understand, and even if done properly it still remains a possible week spot to a wall failure.

you can set up a gravity feed outlet pipe over the wall and to a tap.

has the dam been through any major storm water dumps being in a gully?

len

purplepear
10-09-2009, 05:22 AM
Hello gbell
at Bills place at tylgum, he cut the wall to fit pipes. At least Doug did. I have successfully used a syphon system which is a lot less scary. What I did was to pump from a creek up to the dam to fill a two inch pipe with water and the result was to create a syphon down to my garden. The pipe was attached to a star picket in the dam. I had continuous flow and only once in several years did I have to re prime when (in the drought) I run out of water in the dam or at least the level dropped below the pick up.
Regards purplepear
intent-observation-intuition

milifestyle
10-09-2009, 07:23 AM
A mate has a dam with 6 inch gate valve at the bottom and a spill over about 300mm from the top. Its a creek fed dam with larger dams upstream. The upstream dam broke its wall a couple of weeks ago which over flowed the mates dam to white water rapids. The wall stayed in tact and because the gate valve was open and the spill over large enough the dam wall, which is only bout 3 months old stayed in tact.

ho-hum
17-09-2009, 09:39 PM
Hiya,

If you have a functional dam wall then it is really best to protect the integrity of it. If you set up a decent 2'' syphon. For example, work out much 2'' pipe can hold 750l of water. Spend the time to get a syphon happening and have a decent gate valve set up at the bottom. Purchase or get a 1000l firefighting/water unit. Most places that have room for a damn really need a firefighting/compost tea tank & pump system.

Once established this pipe can be used for high water levels and irrigation. If you have the slope make sure you dont create an erosion zone. If your water isnt corrosive you can set up a great dripper system downhill for a line or two of trees. Don't forget your recharge area uphill is a great place to establish plants too..

cheers,

ho-hum

gbell
18-09-2009, 08:59 AM
OK, so the recommendations are (if I'm understanding):

1) Leave the wall alone
2) Run 2" irrigation pipe up and over the dam wall.
3) Run that pipe to a 1000L tank down below (why?)
4) Set up a siphon between the tank and the dam.

Not sure why I need the 1000L tank in the system. Wouldn't that make it harder to re-do the siphon if the dam runs dry?

gardenlen
19-09-2009, 05:01 AM
sounds like about it gbell,

when you run the siphon which can go to a watering trough if you like you use a floating ball cock, so as the level empties it refills again also need a non-return valve so if something happens water is stopped from running back out of the gravity feed pipe. also somewhere i remember seeing how someone had set up a feed/bleed part so they could pour water back into the pipe to cause if to siphon a gain, like a 't' section with a removable capped pipe sticking up i think it was?

len

gbell
04-01-2013, 08:15 AM
I've implemented a siphon with 40 mm ag pipe, some valves, and a t-join to bleed it. This is more expensive than Purple Pear's suggestion of petrol-pumping up from the outflow (plus, where to get that water from?) But, it allows me to prime the siphon manually but removing the cap and dumping water into the system until full.

Unfortunately, it has proven very temperamental. As anybody who's played with siphons knows, if the flow isn't great enough, air can work its way back up and break the siphon. To solve this, I used a bucket as an airlock, as below:

https://lh5.googleusercontent.com/-kXyQjEPJf-g/UOYPm2WTRII/AAAAAAAABHw/hXMNK2c-qps/s800/siphon.png

It works, but two problems:

1) There's a continuous flow of "champagne bubbles" coming out in the bucket, and I can't for the life of me figure out where air is getting into the system.

2) It ran for about 5 hours, which is pretty good, but then stopped, while the foot valve was still under water. I believe there's still enough of a height differential for the siphon to keep going. This means it failed due to (finally) too much air. This makes it too risky to use for stock watering.

Has anybody actually implemented one of these, and do you have any advice from your experience?

sweetpea
10-01-2013, 04:35 AM
My sister has a large natural pond with a man-made dam in a gully, someone before she moved there, made an overflow by cutting part of it away. It has been nothing but a nightmare because at least once a winter there's enough water needing to go out that it tears away there and damages, and "keeps cutting!" as my father says. Don't touch a good dam wall!

I use a syphon to get water from my pond over the wall, down to the crop below the pond. The pond is about halfway up the side of a hill. It works really great every time, and be sure to use filters on the pond end so crud, leaves, duckweed, algae, little frogs, pollywogs don't get sucked into the pipe. I use pantyhose-style knee-hi legs, which have to be changed about once every two weeks during the hottest part of the summer because they catch algae, etc. But they have elastic around the top and stay on the pipe really well.