Is a scoop strainer mandatory for raw water intake through hull?

[rhumbunctious]

Is a scoop strainer such as the following mandatory for a raw water intake through hull?

or can a more basic strainer such as the following work just fine?

???

 

[Porthandbuoy]

Not mandatory, but advisable. Blunt edge forward, slots to the rear, as well.

T'other is more like the heads inlet seacock strainer.

 

[Stu Jackson]

Worst thing you can do. Just creates more places for bad stuff to grow. Makes it harder to rout out your thru hull with a simple dowel through an open seacock.

 

[Tranona]

Neither. These went out of regular use years ago. A straight inlet with a water strainer such as a Vetus immediately above it is the most common way now. That way any blockage is above the waterline and can be cleared from inside or if it is over the inlet can be rodded out.

 

[guernseyman]

Better an inboard strainer, removable for clearing and allowing the thru hull to be poked clear.

 

[Bosun Higgs]

Neither. These went out of regular use years ago. A straight inlet with a water strainer such as a Vetus immediately above it is the most common way now. That way any blockage is above the waterline and can be cleared from inside or if it is over the inlet can be rodded out.

Why risk putting a stick down through an open seacock and with water flooding into the boat, when if you use the first type above, nothing can ever stick to the outside?

 

[Skysail]

On balance I think the inboard strainer is preferable. If you do have an external one, be very careful to antifoul inside it; otherwise nasties will grow there and restrict the flow. How do I know....?

 

[Norman_E]

Either type can get choked with marine growth. I have the first type on my engine seacock, and debated removing it before launching. I left it in place but have a piece of steel tube with the end squeezed flat so that in can in need be used to clear at least a some of the slots, working through the flexible pipe from above the waterline.

Rather than removing it completely, would it be better to remove alternate ribs?

 

[Leighb]

Why risk putting a stick down through an open seacock and with water flooding into the boat, when if you use the first type above, nothing can ever stick to the outside?

I would assume that, provided that the inlet pipe rises above the waterline, there is no problem with pushing a stick through to clear it as no water could come in?

Wouldn't work on my boat as the saloon floor is below water level so the pipe could not be long enough.

I have an external scoop type strainer and have had no bother with blockages -- so far.

 

[stuartwineberg]

Agree

Neither. These went out of regular use years ago. A straight inlet with a water strainer such as a Vetus immediately above it is the most common way now. That way any blockage is above the waterline and can be cleared from inside or if it is over the inlet can be rodded out.

+1

 

[Deleted member 36384]

I worked for a few years on a charter fleet and none had grills over the raw water inlet. The boats were mostly mid 1980's Sigma, Westerly, Moody, Saddler and Contessa models. My own boat, a Rival 41, was built in 1974 and I know of one other, neither have a grill over the raw water inlet. Hence, I do not think many designers thought that they were necessary, at least on these yachts.

I have the type in your lower picture over the heads inlets and both need an internal clean to remove marine growth every couple of years.

 

[HermanD]

If you ever had one eel in the inlet, you mount one outside strainer.

 

[pampas]

#2 post

(Blunt edge forward, slots to the rear) NOT if its a internal scoop type.

 

[omega2]

No external strainer, just a 1.5" gate valve, to a blakes sea cock, as stated can be rodded through, or even let the tescoe bags come inside the boat, easily removed, but if outside and under water?? We have a problem Huston!

 

[Porthandbuoy]

Okay. I stand corrected and hang my head in shame for giving what is perceived by some to be bad advice.

Note to self: Remove strainers sometime.




Goes and stands in the corner

 

[prv]

Why risk putting a stick down through an open seacock and with water flooding into the boat

If you design the system inside properly, the opening (hose end, rodding eye, etc) will be above the waterline so no water flooding in.

when if you use the first type above, nothing can ever stick to the outside?

That's a very confident statement. I don't think I would care to rely on it quite so much.

Pete

 

[Stu Jackson]

http://forums.sbo.sailboatowners.com/showthread.php?t=124964

 

[Marsupial]

Why risk putting a stick down through an open seacock and with water flooding into the boat, when if you use the first type above, nothing can ever stick to the outside?

sorry to dissagree but yes it can, we picked up a plastic bag in the marina and it would not let go, had to have the boat lifted to release it, the "handles" had entered the "grating" and stuck there.

There is also something about which way the boot faces, backwards for a yacht forwards for a mobo, a quick look around the boats on the hard here confirms this.

As Tranona says a plain mark one hole seems to be the norm on later boats.