How to Install Posts in the Water for a Dock or Pier
Determine the soil characteristics of the lake, lagoon or stream bed you are installing your piles into., Obtain your pilings., Rent a 2 or 3 inch (5.1 or 7.6Â cm) gasoline-powered water pump, a suction or "pickup" hose long enough to draw water from...
Step-by-Step Guide
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Step 1: Determine the soil characteristics of the lake
Rock will be unyielding, obviously, so this technique will not work, and silty, muddy material will not support the pier structure.
Sandy material is ideal for jetting pilings, but any firm soil will allow jetting. -
Step 2: lagoon or stream bed you are installing your piles into.
These need to be chemically treated to resist rot, usually with sodium pentachloride at .25%, copper-chlorinated arsenate, at .25%, or creosote.
You will need the pilings to be large enough to attach your support joists to, and long enough to allow them to be sunk deep enough in the round to bear the weight you will be putting on them.
Because you will achieve a different load bearing in different bottom materials, there is no rule of thumb for how deep the piling should be installed, but a minimum of four feet would be reasonable if the piling seems "tight"
or secure.
Try for 6' deep in the sand.
Mark the piles with spray paint at 12" intervals so you know the depth of penetration. 6" to 8" diameter piles are used for small (up to 10,000 lb.) watercraft docks. , An alternative to the pump may be connecting to a fire hydrant, if your local utility will allow you to do so, but a back flow preventer must be used in this case. , Depending on the depth of the pile jetting, this will be a 6' to 12' section of 3/4" pipe with an elbow at one end to attach your pump discharge hose.
That will supply water for jetting.
Connect a reducing bushing or flatten the other end.
That will be your "jet"
providing a stream of water to wash and blow out a hole for the piling to set into. , Tie a length of builder's line from the stake on shore to the stake in the water, and measure the distance from piling to piling, marking them with a permanent marker.
The string line should be about the height above water you will want the top of the pilings to be when they are set.
Set out the offset from other pilings with a 45 degree plastic square, and cut to length bamboo poles snap-tied to it. , The water rushing through the jet pipe will "blow out" a hole underneath the piling, and it should immediately begin to sink.
By moving the jetting pipe around the bottom of the piling, you can guide the direction that the hole is created underneath it.
By moving the jet from one side of the piling to the other, you can "steer" it down straight.
In good material, such as sand, you can jet down a piling in a few seconds, provided you have sufficient water pressure and velocity.
The sand is seldom clean and can contain roots, mud etc. so use a 6' ice scraper to break through.
Roots can cause piles to seat off their desired location.
The pilings float so you may need to push them down to obtain better depth (see tips below). 12'x 6" or 16'x 6" pilings can be stood up easily by one or two persons.
Up to a 12'x 8" dia. piling can be installed with two people.
Larger piles need a crane as they weigh 500 lbs (20' x 8"dia.).
A crane can be built simply with a 24' pontoon boat, 2" steel water pipe, steel cable and a 12v car winch.
The design and manufacture would have to be checked for safety before using it.
When using a crane you need one person jetting, one guiding the pile and digging and a crane operator.
Try to work when the water is calm.
However if the pile is out of line, it is easy to jet it out and put it in the correct position.
It is possible to install 10 or more piles per day depending on factors such as depth required, bottom make up, sufficient help handling pilings, etc..
Protective wet suit pants, boots and gloves should be used to prevent abrasion loss of skin especially when you have been in the water for some time. , Once the settling occurs, it will be difficult to change the orientation of the piling. , This may not be necessary in sand as it settles back in the hole pretty quickly. -
Step 3: Obtain your pilings.
-
Step 4: Rent a 2 or 3 inch (5.1 or 7.6Â cm) gasoline-powered water pump
-
Step 5: a suction or "pickup" hose long enough to draw water from the lake or seawater that you are installing pilings in
-
Step 6: and a discharge hose long enough to reach the end of the pier from the location where you plan to set the pump.
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Step 7: Build a "jetting pipe".
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Step 8: Lay out the location of your pilings by using a 2X4 wood stake driven into the ground on the bank
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Step 9: and another driven into the pond bottom beyond the location of the last piling.
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Step 10: Stand a piling on end in the water
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Step 11: raise your jet pipe alongside it
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Step 12: and turn on the pump.
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Step 13: Plumb up the piling with two spirit levels and a bungee cord
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Step 14: and quickly make sure it is vertical before the soil settles back into the hole.
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Step 15: Wash sand or dirt back around the piling with the jetting pipe after the piling is sunk
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Step 16: to refill the hole what you washed out.
Detailed Guide
Rock will be unyielding, obviously, so this technique will not work, and silty, muddy material will not support the pier structure.
Sandy material is ideal for jetting pilings, but any firm soil will allow jetting.
These need to be chemically treated to resist rot, usually with sodium pentachloride at .25%, copper-chlorinated arsenate, at .25%, or creosote.
You will need the pilings to be large enough to attach your support joists to, and long enough to allow them to be sunk deep enough in the round to bear the weight you will be putting on them.
Because you will achieve a different load bearing in different bottom materials, there is no rule of thumb for how deep the piling should be installed, but a minimum of four feet would be reasonable if the piling seems "tight"
or secure.
Try for 6' deep in the sand.
Mark the piles with spray paint at 12" intervals so you know the depth of penetration. 6" to 8" diameter piles are used for small (up to 10,000 lb.) watercraft docks. , An alternative to the pump may be connecting to a fire hydrant, if your local utility will allow you to do so, but a back flow preventer must be used in this case. , Depending on the depth of the pile jetting, this will be a 6' to 12' section of 3/4" pipe with an elbow at one end to attach your pump discharge hose.
That will supply water for jetting.
Connect a reducing bushing or flatten the other end.
That will be your "jet"
providing a stream of water to wash and blow out a hole for the piling to set into. , Tie a length of builder's line from the stake on shore to the stake in the water, and measure the distance from piling to piling, marking them with a permanent marker.
The string line should be about the height above water you will want the top of the pilings to be when they are set.
Set out the offset from other pilings with a 45 degree plastic square, and cut to length bamboo poles snap-tied to it. , The water rushing through the jet pipe will "blow out" a hole underneath the piling, and it should immediately begin to sink.
By moving the jetting pipe around the bottom of the piling, you can guide the direction that the hole is created underneath it.
By moving the jet from one side of the piling to the other, you can "steer" it down straight.
In good material, such as sand, you can jet down a piling in a few seconds, provided you have sufficient water pressure and velocity.
The sand is seldom clean and can contain roots, mud etc. so use a 6' ice scraper to break through.
Roots can cause piles to seat off their desired location.
The pilings float so you may need to push them down to obtain better depth (see tips below). 12'x 6" or 16'x 6" pilings can be stood up easily by one or two persons.
Up to a 12'x 8" dia. piling can be installed with two people.
Larger piles need a crane as they weigh 500 lbs (20' x 8"dia.).
A crane can be built simply with a 24' pontoon boat, 2" steel water pipe, steel cable and a 12v car winch.
The design and manufacture would have to be checked for safety before using it.
When using a crane you need one person jetting, one guiding the pile and digging and a crane operator.
Try to work when the water is calm.
However if the pile is out of line, it is easy to jet it out and put it in the correct position.
It is possible to install 10 or more piles per day depending on factors such as depth required, bottom make up, sufficient help handling pilings, etc..
Protective wet suit pants, boots and gloves should be used to prevent abrasion loss of skin especially when you have been in the water for some time. , Once the settling occurs, it will be difficult to change the orientation of the piling. , This may not be necessary in sand as it settles back in the hole pretty quickly.
About the Author
Tyler Robinson
Specializes in breaking down complex crafts topics into simple steps.
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