Empty Raw Water Strainer

[viva]

The water strainer on my boat was one of the bronze pillar affairs fitted low down in the bilge on top of the seacock which made it difficult to reach and check. During the summer I had an engineer fit one of the Vetus plastic strainers with the clear lid, thus making it much easier to check. The engineer mounted the new strainer on the bulkhead of the engine compartment and above the waterline. He said that although there is a U tube anti-siphon device it was safer to have the strainer above the water line. My question is that before starting the engine, the bowl of strainer is empty. As soon as the engine is started water is quickly sucked in and swirls round the bowl and all is fine, but isn’t there a problem that the impeller will be sucking a couple of feet of air before the bowl fills? Is this a problem for the impeller? I believe on earlier boats the strainer was always full before starting.

 

[sailorman]

seal the "O" ring with silicone grease, there must be a slight air leak causing loss of water

 

[vyv_cox]

Are you sure it is piped the right way around? The reservoir should remain full when the engine stops, unless there is a leak on the downstream side, i.e. from the pump itself or the hose connections to it.

Don't understand the anti-siphon info. This should be after the pump, either between it and the engine/heat exchanger or between engine/heat exchanger and exhaust manifold.

 

[Rivers & creeks]

Interesting, ours does exactly the same. Strainer is above the water line, all pipes nipped up etc. I'll try the silicone grease.

 

[fisherman]

I think that when you stop the engine the water drains down from the strainer in both directions: it should settle at waterline level, if this is above the impellor then there will be water present at startup. Easy to obtain 'run dry' impellors anyway:

http://www.amazon.com/Globe-Marine-13554-0001-GTA-12457-00-119773-42600-01/dp/B00C9DKRMM

 

[vyv_cox]

Interesting, ours does exactly the same. Strainer is above the water line, all pipes nipped up etc. I'll try the silicone grease.

I often take the lid off mine, the water remains exactly where it is, right to the top of the container. When I flush with fresh water at the end of the season (ashore) I simply run water into it from a hose pipe with a trigger spray gun, let the pump pull it down, then top up again. Easy to keep this up for a couple of minutes.

 

[Pagetslady]

Are you sure it is piped the right way around? The reservoir should remain full when the engine stops, unless there is a leak on the downstream side, i.e. from the pump itself or the hose connections to it.

Don't understand the anti-siphon info. This should be after the pump, either between it and the engine/heat exchanger or between engine/heat exchanger and exhaust manifold.

Hope you don't mind me jumping in on this thread with a similar problem. I fitted a Beta 35 this Jan and I needed to increase the sea cock and pipe sizes, so I fitted a new filter which also has a clear top, I have been surprised that there is only ever a small amount of water in the bottom of the filter I am still getting water out with the exhaust but would like to have more however the engine runs fine. I am now wondering if I have plumbed the filter in correctly the water comes in to the inside of the filter and I assume goes to the pump outside the filter insert.
Mike

 

[Stork_III]

Hope you don't mind me jumping in on this thread with a similar problem. I fitted a Beta 35 this Jan and I needed to increase the sea cock and pipe sizes, so I fitted a new filter which also has a clear top, I have been surprised that there is only ever a small amount of water in the bottom of the filter I am still getting water out with the exhaust but would like to have more however the engine runs fine. I am now wondering if I have plumbed the filter in correctly the water comes in to the inside of the filter and I assume goes to the pump outside the filter insert.
Mike

That sounds right, just as my VP strainer, which remains full even with the top off.

 

[Pagetslady]

That sounds right, just as my VP strainer, which remains full even with the top off.

When I had the VP one if the sea cock was open it would drain with the top off. But having looked at some exploded pictures of the Vetus one there seems to be a pipe coming up to the top of the filter which mine has not with this the filter would remain full to the top of this pipe unless there was a leak on the pump side. Has anybody got a strainer at hand and check if the inlet is extended to the lid please
Mike

 

[Stork_III]

When I had the VP one if the sea cock was open it would drain with the top off. But having looked at some exploded pictures of the Vetus one there seems to be a pipe coming up to the top of the filter which mine has not with this the filter would remain full to the top of this pipe unless there was a leak on the pump side. Has anybody got a strainer at hand and check if the inlet is extended to the lid please
Mike

On my VP strainer the inlet pipe is near to the top with outlet a base. so water passes through filter inside to out. It stays full provided inlet seacock is in water.

Like this cutaway of a Vetas one. http://www.vetus-shop.com/vetus-raw-water-strainer-type-140-inlet-and216-19mm-p-1019.html

 

[viva]

Vyv yes you are correct about the anti-siphon tube. It is on the exhaust side of the pump and so is irrelevant to this thread. I agree with Fisherman, that, if the sea cock is open, I would have thought the water would drain back to sea level. The pump is able to suck the water in from the seacock up to the strainer with a good flow. So I don't think there can be an air leak and Wouldn't I see a water leak? as for the run dry impellers they don't seem to have a good review on Amazon

 

[Halo]

Call me Mr paranoid but when my inlet strainer is empty and I am ready to start I shut off the seacock, take the lid off the strainer, fill the strainer and pipes with water as full as possible, screw on the lid and open the seacock. If it drains quick I know the lid is leaking and i tighten up or apply an oil film OR neat washing up liquid to the seal, refill and try again.
Once sealed properly the water stays in the system from week to week but it does seem to need a bit of sorting at the start of the season or whenever the lid is taken off

 

[pvb]

Vyv yes you are correct about the anti-siphon tube. It is on the exhaust side of the pump and so is irrelevant to this thread. I agree with Fisherman, that, if the sea cock is open, I would have thought the water would drain back to sea level. The pump is able to suck the water in from the seacock up to the strainer with a good flow. So I don't think there can be an air leak and Wouldn't I see a water leak? as for the run dry impellers they don't seem to have a good review on Amazon

There are 2 types of Vetus plastic strainer. Type 140 has the inlet tube rising almost to the top of the strainer body; with this, if the lid is removed, most of the water will remain in the strainer if the lid is removed (unless the raw water pump doesn't seal very well). However, type 330 has the inlet tube ending at the bottom of the strainer body; with this one the water will drain away if the lid is removed. The neoprene ring on the lid should be lubricated to ensure a good seal.

 

[Pagetslady]

Hi I have noticed that there is a difference between the FTR 140 and the FTR 330 which is a larger bowl and doesn't have the inlet pipe right up to the lid, which is like mine so I guess mine is the 330, so I can only assume that my problem is that the lid is not completely sealing and allowing the water to go back to sea level. I will sort this out tomorrow, I suppose that if there is a leak in the lid seal then the amount of water being sucked up by the pump will be less .
Mike

 

[sailorman]

Hi I have noticed that there is a difference between the FTR 140 and the FTR 330 which is a larger bowl and doesn't have the inlet pipe right up to the lid, which is like mine so I guess mine is the 330, so I can only assume that my problem is that the lid is not completely sealing and allowing the water to go back to sea level. I will sort this out tomorrow, I suppose that if there is a leak in the lid seal then the amount of water being sucked up by the pump will be less .
Mike

A minuscule amount

 

[Rivers & creeks]

There are 2 types of Vetus plastic strainer. Type 140 has the inlet tube rising almost to the top of the strainer body; with this, if the lid is removed, most of the water will remain in the strainer if the lid is removed (unless the raw water pump doesn't seal very well). However, type 330 has the inlet tube ending at the bottom of the strainer body; with this one the water will drain away if the lid is removed. The neoprene ring on the lid should be lubricated to ensure a good seal.

Indeed. It would be impossible for my Vetus to remain full if you take the lid off because the inlet and outlet are at the bottom. What always surprises me is that the thing doesn't fill up when in use.

 

[Pye_End]

I agree with Fisherman, that, if the sea cock is open, I would have thought the water would drain back to sea level.

Water will only drain if it can be replaced by air - ie. from a leak.

 

[Pagetslady]

Indeed. It would be impossible for my Vetus to remain full if you take the lid off because the inlet and outlet are at the bottom. What always surprises me is that the thing doesn't fill up when in use.

You must have the same on as mine, and it never fills in fact I have to look very closely to see any water flowing
Mike

 

[ianat182]

When fitting a new engine in my boat a few years ago I also changed the water strainer to a much cheaper one from Force4 Chandlery. In the instructions for fitting it stated that it should be at least 8" above the outside water level. We worked it out by taking the inlet pipe with the seacock opened, to the level that water just started to flow from the end and worked out the 8" above this 'manometer' level.
The bowl is always empty at startup but only a couple of revolutions are sufficient to get water from the exhaust ,and the bowl becomes about 90% filled all the time.

The only time I've had overheating problems is when there has been an excess of seaweed of all types and the masses of autmn leaves currently on the Hamble, that are trapped by the efficient filter chamber.
As the chamber is at eye level when on my knees it is a simple job to clear and/or check visually.

Part of our shutting down routine is to empty the filter bowl after each sail/motoring trip,and turn the sterngland greaser at the same time ; I do not close the seacock to the to the raw water winter or summer afloat.


ianat182

 

[Flossdog]

I, too replaced my brass column thingy with a Vetus strainer and it has been excellent. It is mounted under the companionway steps so that the natural water lever is half an inch below the top and where I can see the water coming into it. Water level therefore wouldn't drop when engine idle but I have an issue that I would be interested to hear comments from the experts here. Two issues really, the first which is not so serious is when sailing well heeled to starboard, the water in the strainer drops out and empties if the seacock is not closed. I just have to remember to close it when engine is switched off and I am in for some lively sailing. Then remember to turn it on again!

The other issue is that when motoring in choppy conditions, i.e. F5-6 in open sea, the strainer water level drops as it accumulates air. It sucks in bubbles that are running along the bottom of the boat. The strainer can "empty" in 20 mins. Now, my water intake was the bronze scoop type with bars. However, having sucked in a load of weed (there is a lot of it in the various estuaries where I sail) into the bronze strainer several times, I could not "rod" it out whilst afloat (due to the bars) and I had to dry out to clear it. This was not on so I cut away the scoop and bars and the intake is now flush. It is now easy to "rod" through the intake tube and clear any weed. In fact I have never had to do it as the weed just collects in the Vetus strainer instead. But I still suffer with the accumulation of air in the strainer. My question is, why does this not happen on other people's boats?