Height of Raw Water Strainer above waterline

Habebty

Habebty

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Is there an optimal height for a raw water strainer. Is there any preferred relationship with the waterline?
I have the opportunity to reposition the strainer whilst renewing the intake skin fitting and would like to move it above the waterline.
Any issues I should be aware of?

cheers
 
The minimum is 15cm - see the Vetus catalogue www.vetus.co.uk page 156. Useful to locate the filter directly above the intake so that you can use a rod to clear any blockage in the intake.
 
VicS said:
Page 54 I think!

http://viewer.zmags.com/publication/fd2b8fee#/fd2b8fee/54 if the link works


But any idea why the filter should be at least 6" above the waterline.

.
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My 2009 paper catalogue has p156 - 54 is windscreen wipers!

As to the reason, I know not but am quite happy to accept it as some of the biggest criminals ever have got away with only obeying orders!

Actually I assume it is so that you can safely take the cap of to clean it without the possibility of water sloshing up. I would have though a maximum is more critical as the pump has to lift the water - but on my Bavaria it must be at least 40cm above the waterline and works OK!
 
Mine is below the waterline, under the floor in the cabin, so no choice really as there is no room in the engine bay. It is not a problem as long as I remember to close the seacock before I unscrew the top!!

I can see that it would ideally be above the waterline as it is easier to clear out any debris.
 
My 2009 paper catalogue has p156 - 54 is windscreen wipers!
Click to expand...
But the link now takes you to the on-line 2010 catalogue. (in that 156 is battery cables terminals and boxes!)

The old fashioned bronze strainers screwed directly on top of the inlet gate valve and were almost certain to be below the waterline.

The higher above the water line they are fitted the greater the risk of air leaks and loss of pump prime.

However 15cm min is what they say!
 
For years the paper and on line catalogue have been the same. How dare they change it without asking me! (Although I have not got a copy of the 2010 catalogue to check) Perhaps that is why their prices have gone up by more than 30% in the last couple of years!
 
I have the Vetus FTR330 type and it would be impossible in my boat to have it 15cm above the waterline unless I moved it out of the engine compartment. In fact the waterline is about 1/2" above the bottom of the strainer and it works fine like that.

Advantages of this type of filter are that the clear top allows you to see that water is being pumped into the engine without having to hang over the stern to look at the exhaust, and the strainer can be removed for cleaning without needing to shut the seacock. Also, as somebody has mentioned, having it directly over the seacock means the intake can be rodded through with a stick.

Another plus is that when running the engine with the boat ashore you don't need to disconnect anything to get a water supply into the engine. Just take off the filter cover and let the shore supply hose run into the filter housing. Any excess water runs down through the seacock
 
One very good reason would be security. It is generally considered correct practice that all hose connections to skin fittings should have 2 clamps minimum in case one fails. I believe your water strainer is a Vetus with a screw top lid . How secure should we consider this arrangement ? I should think this is the reason why Vetus specify 15cm .
BTW Like Wherry, I also own a Sadler 290 which has its raw water inlet via the saildrive leg. (Wherry's inlet as built was a skin fitting). I have experienced engine overheating which might be due to clogging by mud because I have drying mooring. I plan to fit a skin fitting in the bottom of the galley cupboard adjacent to the engine.
 
parsifal said:
I have the Vetus FTR330 type and it would be impossible in my boat to have it 15cm above the waterline unless I moved it out of the engine compartment. In fact the waterline is about 1/2" above the bottom of the strainer and it works fine like that.

Advantages of this type of filter are that the clear top allows you to see that water is being pumped into the engine without having to hang over the stern to look at the exhaust, and the strainer can be removed for cleaning without needing to shut the seacock. Also, as somebody has mentioned, having it directly over the seacock means the intake can be rodded through with a stick.

Another plus is that when running the engine with the boat ashore you don't need to disconnect anything to get a water supply into the engine. Just take off the filter cover and let the shore supply hose run into the filter housing. Any excess water runs down through the seacock
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I have this type of filter, and it also is currently just below the waterline so was wondering if it should be moved. Also it would be difficult to position it 15cm above the waterline but I could probably achieve 1-2 cm above the waterline.

Just needed to know if there were any hard and fast rules on the subject.:)
 
My Bavaria has a saildrive, but uses the normal water intake therough the leg, so having the filter immediately above for cleaning is largely irrelevant. The Vetus strainer is on the opposite side of the engine bay with a long run of hose then a shorter run to the seawater pump. It works as a strainer because we have o clean it - usually weed and is easy to get at. so not sure it has to be close to either intake or pump, but in a place where access is easy for cleaning.
 
wherry said:
I have this type of filter, and it also is currently just below the waterline so was wondering if it should be moved. Also it would be difficult to position it 15cm above the waterline but I could probably achieve 1-2 cm above the waterline.

Just needed to know if there were any hard and fast rules on the subject.:)
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I think it's handy to be able to take the lid off without shutting the seacock. Also if the top of the casing is below the waterline and the lid was cracked (being plastic it might do one day) and the seacock was accidentally left open when you went ashore, your boat could fill up.

Also, if the filter is left full of water it might crack if there was a frost.
 
wherry said:
I have this type of filter, and it also is currently just below the waterline so was wondering if it should be moved. Also it would be difficult to position it 15cm above the waterline but I could probably achieve 1-2 cm above the waterline.

Just needed to know if there were any hard and fast rules on the subject.:)
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On my Bavaria with a Vetus strainer, the water level in the strainer is about 1 cm below the lid. You can therefore take the lid off to clean the strainer etc. without problem, in flat calm at least. I've not tried in a rolly berth.

I would agree that the strainers with the transparent lid are well worthwhile. Not only can you see the water circulating (and how fast), you can also see if it needs cleaning without having to take it apart.
 
wherry said:
Is there an optimal height for a raw water strainer. Is there any preferred relationship with the waterline?
I have the opportunity to reposition the strainer whilst renewing the intake skin fitting and would like to move it above the waterline.
Any issues I should be aware of?

cheers
Click to expand...

You will soon find out the folly of having it anywhere except at the seacock - when you need to clear blockage.

I quite often have to close the intake ... remove strainer, clean it of ****e, replace and get on with boating ... I have a 1m draft in a mooring with 1m water !

Fit strainer anywhere else and how the hell will you clear any blockage once been aground etc. ?

Sorry but anything other than immediately on the seacock is daft .. stupid ... whatever you wish to call it. Old seahand to ??
 
If it is installed above the through hull it is easy to remove the hose from the intake side of the strainer and push a rod or smaller hose through to clear a clog. Especially if the through hull is the straight through type instead of the kind with a grate over.
 
Refueler said:
You will soon find out the folly of having it anywhere except at the seacock - when you need to clear blockage.


Fit strainer anywhere else and how the hell will you clear any blockage once been aground etc. ?
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As stated above by Tranona: "Useful to locate the filter directly above the intake so that you can use a rod to clear any blockage in the intake. "

and by me: "Also, as somebody has mentioned, having it directly over the seacock means the intake can be rodded through with a stick."


Essential item of equipment on my boat:

Stick, Chinese, bamboo, rodding through, 1 metre long.


Technique;

Remove lid from Vetus filter. Insert stick down through centre hole, inlet pipe and seacock. No need to close seacock or stop the engine (if you're quick). Remove stick. Replace filter lid. Wipe stick.

What's difficult about that? :confused:
 
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Refueler said:
Sorry but anything other than immediately on the seacock is daft .. stupid ... whatever you wish to call it. Old seahand to ??
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Rather extreme position, Nigel! I installed my first Vetus filter in 1992, immediately above the intake for that very reason. NOT ONCE since then have I had cause to clear the inlet. Why? because I am afloat in a marina all the time and I never ground in mud. Despite that on my new installation with the intake in a different position, I have still mounted the filter immediately above the intake. Why? because it is just as easy to do that as mount it elsewhere. However I would not have got too worked up about it if there was no space to do that.

As I pointed out on my Bavaria it is a long way from the intake, but as you cannot "rod" a saildrive, the alternative that some people say works is to use the dinghy pump to blow anything out. However, again I have never had the intakes blocked, only weed being sucked up into the filter which is easy to clean because it is well above the waterline. If I sat down in mud regularly with that boat I would have two intakes, one through the leg and the other through a skin fitting and a Y valve to switch from one to the other. More than one way of skinning a rabbit!
 
Also remember if the strainer is above WL it will be under suction when running, so if it leaks the engine will pump air instead of water. Also it may not self prime.
Not a problem if you are aware of these things.
A length of stiff 'garden wire' the green plastic coated stuff is very good for clearing the intake if its not exactly straight to the seacock/skin fitting.
 
anniebray said:
It is generally considered correct practice that all hose connections to skin fittings should have 2 clamps minimum in case one fails.
Click to expand...

Actually the general consensus now is to fit 3 clamps per hose, best be safe.
 
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