Pick up tube for watermaker?

[Chotu]

Originally Posted by Tellie

Hi Chotu,

Sorry to hear of your medical issues, i hope all is much better now.

Remind me again why there are no thru hulls on your boat? The answer is simple for a boost pump. But a proper thru hull is needed and is going to make your watermaking life with the CHE much easier and far more convenient. This over the side stuff is creative but you'll need a continuous duty pump for this, most cheap pumps won't be up to then task a watermaker will demand.

Hi Tellie.

it looks like we did already have some discussions further back in the other thread that is linked above. I forgot because of the medical issues. That year was a blur. Thanks for the good wishes. Things are great now. Feeling good.

I definitely didn’t envision any cheap pump. A continuous duty submersible that supplies 2.7 gallons per minute or more, at a reasonably low PSI was the idea.

The reason I don’t have thruhulls is because I don’t like them. They are a nuisance. They are a hassle. They make life difficult. you have to clean them out. You have to replace hoses. You have to make sure the seacock remains viable and exercise them. You have to close them when you leave the boat. You have to replace salt water pumps constantly. You have to worry about zincs. They open up a rats nest of problems that you don’t need to deal with when you don’t have them. It’s far superior not to have them. It makes all maintenance significantly easier. Everything can be just replaced easily with something off the shelf. No need for annoying difficult projects. I have a huge chest freezer. A real refrigerator that you open the door on. 36,000 BTUs of air conditioning. And they’re never going to break. They’re never going to need maintenance. No seacocks. That’s my stance. And I’ll stand by it.



But on the watermaker topic, since I only have a 24 inch maximum depth even at the very center of the hulls in a fore and aft sense, any thruhull I put in is going to suck air when I am underway. Especially toward the stern where the water maker is being installed. Back there, I have maybe 12 inches. Maybe. And I'm capable of 20 knots in extremely favorable conditions. Easily do 12-15 all-day long.

Water will only be made when I am anchored. Not underway.

So a continuous duty submersible pump at the end of the little sipping tube should do the trick I would think. As long as those surflo pumps are supplied with the proper water they need, they won’t know if they are being fed by a seacock or another pump.

But I definitely want to save my questions with you for when I am commissioning this water maker. I am bound to run into some issues. It’s an oldie and it’s been sitting around.

[rslifkin]

For the pump, if the boost pump is something like a typical fresh water system pump, they can lift water a couple of feet. No need for a submersible pump on the pickup.

With the hull depth concern, maybe the best option is a tube that's fixed mount in the outboard wells, but can be moved vertically. Then if you want to use it underway, you can just extend it down an extra foot to make sure it's not sucking air.

[Chotu]

Originally Posted by rslifkin

For the pump, if the boost pump is something like a typical fresh water system pump, they can lift water a couple of feet. No need for a submersible pump on the pickup.

With the hull depth concern, maybe the best option is a tube that's fixed mount in the outboard wells, but can be moved vertically. Then if you want to use it underway, you can just extend it down an extra foot to make sure it's not sucking air.

This could be true. I’ll have to think about it a little bit. Really I want to make sure it’s designed for my use case. Whatever that may be. I think it’s just at anchor.

my sister ship for instance got from South Florida to the Outer Banks in two days. Left on a Monday arrived on a Wednesday.

meanwhile, it just took me a whole month to do the same thing by motoring up the intercoastal at 5 or 6 kn. Around in circles against the current. Sleeping each night.

So just due to the sheer nature of this boat, I’m sure it will be spending a lot more time at anchor than underway. More than even the average boat. Because the passages are shorter.

[Franziska]

Originally Posted by Chotu

This could be true. I’ll have to think about it a little bit. Really I want to make sure it’s designed for my use case. Whatever that may be. I think it’s just at anchor.

my sister ship for instance got from South Florida to the Outer Banks in two days. Left on a Monday arrived on a Wednesday.

meanwhile, it just took me a whole month to do the same thing by motoring up the intercoastal at 5 or 6 kn. Around in circles against the current. Sleeping each night.

So just due to the sheer nature of this boat, I’m sure it will be spending a lot more time at anchor than underway. More than even the average boat. Because the passages are shorter.

Be careful pick up tube in outboard well has probably a higher risk of accidental oil contamination.
Something desalinator membranes surely do not like..

Sent from my MHA-L29 using Cruisers Sailing Forum mobile app

[SailingHarmonie]

Your idea of a submersible centrifugal pump is actually probably the best of a set of mediocre choices

You have gotten a lot of very bad advice here. Here is the issue that people don't get:

Almost all self-priming pumps are positive displacement pumps. They pump a FIXED volume of water based on pump speed (more or less) against whatever pressure they can make.

If you are using a positive displacement pump as a boost pump to a water maker and the pump does not feed EXACTLY the right amount of water, you will either starve the watermaker pump, or the pressure will rise to the point that the boost pump will stall and pop a breaker, or fail.

Water is incompressible. If a positive displacement boost pump tries to pump 2.51 gallons into a system that can only take 2.50 gallons, the pressure will spike and something will break.

Diaphram pumps, NO! they will not work here. Flexible impellers will work--kind of-- but have a very short life on the impeller if they feed enough water and use backflow though the vanes to control the pressure.. Fresh water system pumps also will not work without a system to control and maintain the pressure on the outlet that I suspect you really don't want.

There are ways around this problem, but they are fussy, and will take way more maintenance than a seacock, so I assume they are not of interest.

Of course you are trading the trivial maintenance on a single through hull for the hassle of a submersible pump running in salt water, that you have to drop overboard and then recover, and store every time you want to make water. But that's what you want...

[Chotu]

Originally Posted by SailingHarmonie

Your idea of a submersible centrifugal pump is actually probably the best of a set of mediocre choices

You have gotten a lot of very bad advice here. Here is the issue that people don't get:

Almost all self-priming pumps are positive displacement pumps. They pump a FIXED volume of water based on pump speed (more or less) against whatever pressure they can make.

If you are using a positive displacement pump as a boost pump to a water maker and the pump does not feed EXACTLY the right amount of water, you will either starve the watermaker pump, or the pressure will rise to the point that the boost pump will stall and pop a breaker, or fail.

Water is incompressible. If a positive displacement boost pump tries to pump 2.51 gallons into a system that can only take 2.50 gallons, the pressure will spike and something will break.

Diaphram pumps, NO! they will not work here. Flexible impellers will work--kind of-- but have a very short life on the impeller if they feed enough water and use backflow though the vanes to control the pressure.. Fresh water system pumps also will not work without a system to control and maintain the pressure on the outlet that I suspect you really don't want.

There are ways around this problem, but they are fussy, and will take way more maintenance than a seacock, so I assume they are not of interest.

Of course you are trading the trivial maintenance on a single through hull for the hassle of a submersible pump running in salt water, that you have to drop overboard and then recover, and store every time you want to make water. But that's what you want...

That’s a very good post.

clear, concise, to the point.

did a good job of explaining the difficult nature of the various types of pumps feeding into the diaphragm displacement pumps. Very nice actually.

yes. It’s what I want. I want to drop the tube when I need to make water. Which is not very often.

I agree about the outboard well. You can see a ring of carbon around them anyway just from exhaust and all of that. Definitely not something I want to be drinking out of.

[SailingHarmonie]

Originally Posted by Chotu

That’s a very good post.

clear, concise, to the point.

did a good job of explaining the difficult nature of the various types of pumps feeding into the diaphragm displacement pumps. Very nice actually.

yes. It’s what I want. I want to drop the tube when I need to make water. Which is not very often.

I agree about the outboard well. You can see a ring of carbon around them anyway just from exhaust and all of that. Definitely not something I want to be drinking out of.

The problem is that watermakers NEED to run often. Every 24 to 48hours. longer than that and "stuff" starts growing in the membranes and clogs them. Y9ou can not run a watermaker once a week and expect good results.

[newhaul]

Originally Posted by SailingHarmonie

The problem is that watermakers NEED to run often. Every 24 to 48hours. longer than that and "stuff" starts growing in the membranes and clogs them. Y9ou can not run a watermaker once a week and expect good results.

I disagree . I ran mine 1 time per week in season . Never any issues . It's all about prefiltering. There is a ( iirc ) 30 micron filter on the pickup that feeds into a 5 micron main prefilter . Been happily running the same membrane for 20 years with no significant loss of production or increase in salt ppm .

[fourlyons]

Originally Posted by newhaul

I disagree . I ran mine 1 time per week in season . Never any issues . It's all about prefiltering. There is a ( iirc ) 30 micron filter on the pickup that feeds into a 5 micron main prefilter . Been happily running the same membrane for 20 years with no significant loss of production or increase in salt ppm .

I wonder, does the temperature of the water matter? You are in Puget Sound, much colder water, and air (during the summer) than where I am.

[andrzej0nl1ne]

To bypass the problem of differential pressure, I wonder if it makes sense to use one pump to fill a bucket or some type of chamber, and have the WM draw its supply from that bucket. Easy to fit an overflow hose to the bucket.

[newhaul]

Originally Posted by fourlyons

I wonder, does the temperature of the water matter? You are in Puget Sound, much colder water, and air (during the summer) than where I am.

Yes I am homeported in puget sound now days .
The watermaker is actually on its 2nd boat . Started its life on my spencer and cruised the sea of Cortez and a couple trips to Hawaii.
The clarity of the water matters more. Hence my filter setup. I buy the 5micron pleated filters by the case for about 5 bucks each so changing frequently is not an issue.
Water temp has more effect on watermaker output. Warmer will produce more water.

[Chotu]

Originally Posted by newhaul

Yes I am homeported in puget sound now days .
The watermaker is actually on its 2nd boat . Started its life on my spencer and cruised the sea of Cortez and a couple trips to Hawaii.
The clarity of the water matters more. Hence my filter setup. I buy the 5micron pleated filters by the case for about 5 bucks each so changing frequently is not an issue.
Water temp has more effect on watermaker output. Warmer will produce more water.

Thanks for the posts. This is good to know. Very encouraging.

[Chotu]

Originally Posted by andrzej0nl1ne

To bypass the problem of differential pressure, I wonder if it makes sense to use one pump to fill a bucket or some type of chamber, and have the WM draw its supply from that bucket. Easy to fit an overflow hose to the bucket.

I’m sure that idea makes sense. But I think it might be more simple just to have a turbine pump that’s pushing from the water up. then there’s no volumetric difference between the pumps. The turbine pump will only push what it can. if it can’t push more, it just stalls.

your harbor is exactly what I am imagining when I have been picturing if I can run this in a harbor or not. Would you run a water maker out in the mornings in your harbor? I know in that far corner by the Hannaford‘s it’s not a good plan. But what about farther out? On an incoming tide?

[newhaul]

Originally Posted by newhaul

Yes I am homeported in puget sound now days .
The watermaker is actually on its 2nd boat . Started its life on my spencer and cruised the sea of Cortez and a couple trips to Hawaii.
The clarity of the water matters more. Hence my filter setup. I buy the 5micron pleated filters by the case for about 5 bucks each so changing frequently is not an issue.
Water temp has more effect on watermaker output. Warmer will produce more water.

I want to add the link to my prefilters
https://www.ebay.com/itm/10-x2-5-Was...edirect=mobile
This is a 6 pack of filters

[torrmundi]

Chotu, look at Johnsons CM10P7-1 (3/4" hose connection) pump. 3.9gpm with a 4.9ft rise, 2.4gpm for a 6.6ft rise. If you need more, use the CM30P7-1, 5.2gpm at 6.6ft rise. Impellor design, magnetic-coupled, circulating pump. The one aspect I'm unclear about is the immersion. They are IP-67 rated, and have both 12V & 24V models. You can get a variety of electrical connection options (fixed leads, connector on the pump body, etc).
https://www.pumpvendor.com/Johnson_C...-1_series.html