Standpipe system on fiberglass boat?

[Nekton73]

I hadn't heard of a standpipe before and am intrigued. If the top of the pipe is above the waterline, how do you get water from it? Is there a suction hose going down into the water somehow?

[Matt Johnson]

It's like any hose leading above the waterline - the pump pulls the water through the standpipe to itself.

[s/v Jedi]

Originally Posted by Panope

It seems that I have been lucky because I open the strainer only twice per year and have never added grease since the original install, 10 years ago. But, thanks for the reminder, I'm greasing it now.

I too was not a fan. I chose that model because with the lid removed, a rod can be passed through vertically. Because it, the stand pipe, and valve are all in alignment, blockages can be cleared without a drop of water coming aboard.

I guess maybe I am now a fan, considering the lack of trouble.

I think it is the difference in climate. They are Vetus strainers and in the tropics the plastic deteriorates until at some point you can’t open them anymore and the plastic shatters.

Vetus is Dutch so not tropical and I think you are in comparable climate

The silicon grease (dielectric grease) is to keep the rubber o-ring in good condition but that too can behave very differently in other climates.

For cleaning your setup is ideal. I also have the large version of that strainer (about 3-4 times as high) and it is still in good working condition while the plastic looks to be the same so I am still not sure what caused them to break… but I had three of them of different installation years in use for genset, watermaker and A/C and they all broke.

[Muaddib1116]

Originally Posted by Matt Johnson

It's like any hose leading above the waterline - the pump pulls the water through the standpipe to itself.

I assume this requires a siphon? so if you clean the strainer you have to somehow prime it after closing it back up?

[noelex 77]

Originally Posted by Muaddib1116

I assume this requires a siphon? so if you clean the strainer you have to somehow prime it after closing it back up?

Having the seacock above the waterline is a significant advantage with standpipes. If the seacock develops a leak it can be be replaced or serviced without hauling the boat, but perhaps more importantly if it develops a leak while you are away from the boat the leak will simply let in air and not flood the boat.

There is no special priming needed for an engine drawing water via a standpipe. Most engine sea-strainers are installed above the waterline.

[s/v Jedi]

Now we got to the point I make one of my more popular recommendations:

The hose between the raw water inlet of the engine’s raw water pump and the sea strainer must be installed so that it comes down to the pump from a point higher than the pump.

If the strainer is at the same level or lower, then first bring the hose up to well above the pump, then down and connect to it’s inlet.

This ensures a column of raw water standing in that part of the hose after the engine is shut down, keeping the impeller flooded so that it is lubricated by that water during the next startup. This maximizes impeller life, especially when the raw water circuit needs to be primed. It can increase impeller life ten-fold.

[Muaddib1116]

Originally Posted by noelex 77

Having the seacock above the waterline is a significant advantage with standpipes. If the seacock develops a leak it can be be replaced or serviced without hauling the boat, but perhaps more importantly if it develops a leak while you are away from the boat the leak will simply let in air and not flood the boat.

There is no special priming needed for an engine drawing water via a standpipe. Most engine sea-strainers are installed above the waterline.

I didn't think impeller driven raw water pumps pushed air well enough to self prime.

[rslifkin]

Typical impeller driven seawater pumps push air just fine and will self prime without issue. With a couple of caveats. As the impeller gets older and stiffer, self priming ability gets worse (especially if you don't have the intake wet to help it prime as Jedi mentioned).



On at least some pumps, self priming ability will go before the impeller starts to fail in other ways or can't pump enough water. And impeller wear is higher while dry, so forcing the pump to self prime regularly will cause more wear.

[noelex 77]

If no air is introduced into the system the standpipe and all associated hoses will remain full of water. So the standpipe normally makes no difference to priming.

If air is introduced, such as when cleaning an above water sea-strainer, whether or not a standpipe is used the impeller will have to pass some air. The impeller is located below the waterline and can normally do this without any problem. Some prefer to fill the strainer with water after cleaning, which is fine. This can be done with or without a standpipe.

[Muaddib1116]

Originally Posted by rslifkin

Typical impeller driven seawater pumps push air just fine and will self prime without issue.

Good to know, thanks.

Originally Posted by rslifkin

(especially if you don't have the intake wet to help it prime as Jedi mentioned).

Yeah, that's what I assumed you would have to make sure of.

[BAD ORCA]

Originally Posted by s/v Jedi

Terms are used in confusing ways. A standpipe comes up to above waterline and is used for discharge. A through hull fitting, a sea chest and a short pipe with a valve below waterline are used for intake.

Correct. Their standpipe comes up above the waterline quite a bit and then has a sea strainer mounted on top like some of the pics posted.

[BAD ORCA]

Originally Posted by SailingHarmonie

It is usually done on fiberglass boats not to deal with Arctic climates, but to reduce the number of hull fittings.

We have a standpipe/seachest on our boat that feeds the engine, generator, two HAVAC pumps, and the watermaker. Reducing what in "normal" practice would be 6 through hulls to one. If properly designed, they work a treat.

Interesting. If i hadnt just spent a small fortune replacing some of my bronze seacocks and thru-hulls i probably would go this route or a standpipe. Really like the idea of only one hole in the boat.

[BAD ORCA]

Originally Posted by thinwater

I'm not seeing how this reduces the chance of freezing. The seachest can still freeze and you still have the many small lines coming off the seachest. If it does freeze you are cooked, and the chance of damamge from freezing may be greater.

Sort of a case of puting all your eggs in one basket, and then watching the basket. Post a link.

It may have something to do with where the standpipe is located? They explain that its mounted as deep and as close to the center of the boat as possible. I suppose if the interior of the boat gets cold enough, your right it wouldnt matter. On their new boat the standpipe is in the cabin where its always heated above freezing so im sure that helps. On previous boat i dont remember them talking much about it.

https://www.youtube.com/watch?v=TyRYzrvMjxM

[Nicholson58]

Sea chest on ROXY. Dual inlets to matching strainers feeds horizontal copper chest (pipe) with multiple outlets.

[myketch42]

I have had 2 aluminum boats both with sea chests. The sea chests were about a 7 by 10 rectangle , flanged above the waterline with lexan covers screwed to the flange , removal of the cover had easy access to the inside of the grate covering the intake area of the hull. all the raw water that was used aboard came thru various pickup tubes in the cover , except the engine that had a supply valve in one of the sides , discharge were thru standpipes above the waterline I always had one less worry than with my fiberglass and thru hulls