Question about short RO membrane

[laika]

The space thing was a real concern for me, too. I'm operating within pretty tight constraints on a 27'. That said, the 44" spectra CHE membrane that I managed to squeeze in there was one of the best things I've done, and I consider it one of the best uses of space on the boat. Having excellent quality water from a proven and highly efficient WM that only runs a few hours every couple days is, IMO, simply fing awesome. If you can somehow find a way to fit a larger one I doubt you will be disappointed.

I had to cut out and re-build a bulkhead under the settee to get it to fit. But looking back on it now, it was a small price to pay.

[Matt Johnson]

Do you have room high under a side deck in the lazarette? Typically an unused space and seems like it would make a nice area for a membrane houising.

Matt

[SV THIRD DAY]

Originally Posted by zboss

I was under the impression that maintenance normally meant pickling the membrane, swapping out the pre filters, flushing the membrane with RO water, and cleaning the filter basket.

You pretty much summed up all the maintenance I'm aware of....

The only maintenance on the pressure Vessels and end caps I know of is to lubricate the o-rings when you change the RO membranes every 5-7 yrs. Fittings need no maintenance and once per year or every 500hrs (I like once per yr) you change the oil in the Hp pump crank case.

[GordMay]

Originally Posted by Madehn

Rich your answers and expertise freely given are much appreciated!!!!!

INDEED!

[Cheechako]

Originally Posted by zboss

Yeah, learning that we could put the membrane unit in the engine room made a big difference. We would have had no way to mount a 40" membrane anywhere in our cabin except of forward locker and that would have taken up too much critical storage space.

Errrr. what do you mean "due to maintenance of all the connecting fittings and end caps"? What kind of maintenance do those components require? I was under the impression that maintenance normally meant pickling the membrane, swapping out the pre filters, flushing the membrane with RO water, and cleaning the filter basket.

It was an inherited unit on a boat I bought. There was corrosion on the aluminum end caps and some of the fittings. I tried to disassemble and the end caps were stuck/corroded in place. I was surprised how cheap a new membrane and tube was. I could have probably fixed it up but decided to just go to the one long membrane as the 3 short ones hadn't been used in a long time anyway. It was a 120V unit but I changed it to engine drive.... and got the weight of the gen set and big 1.5 hp motor out of the catamaran.

[colemj]

Originally Posted by funjohnson

Do you have room high under a side deck in the lazarette? Typically an unused space and seems like it would make a nice area for a membrane houising.

Matt

This is very good advice - and something a lot of us always forget. When I was installing our membranes, I was thinking about all the things that needed to be moved to make space in the area I wanted to mount in, and how we would lose that space. I was just sitting there thinking when I happened to look UP and realize that nothing ever goes in that top 6" of overhead - even when the locker is "full"!

Mark

[zboss]

Originally Posted by colemj

This is very good advice - and something a lot of us always forget. When I was installing our membranes, I was thinking about all the things that needed to be moved to make space in the area I wanted to mount in, and how we would lose that space. I was just sitting there thinking when I happened to look UP and realize that nothing ever goes in that top 6" of overhead - even when the locker is "full"!

Mark

Yes, that was the original plan until I heard that the membranes should not be mounted in the engine area. However, since we have been told that this should not be "that much" of a problem this is now the plan again.

[phorvati]

Originally Posted by zboss

Guys,

I am pricing out the cost of making my own watermaker because I do not have the space necessary to install a 44" or dual 21" elements without significant modification to our boat.

I found these 14" elements and I was thinking of ganging 2 or 4 of them together but since I am just learning about desal I have a few questions:

1) Would just a single 14" element produce drinkable water?

2) I found a diagram of a home built system that had two elements together but I could not determine from the diagram if the elements get hooked in parallel or in series. Which is better? Pro's and Con's?

3) Suppose I wanted to gang together more than 4 elements? Maybe 8? How do I determine the size HP high pressure pump I need?

I also found these for the housing:

2.5" x 14" Fiberglass/FRP Seawater Pressure Vessel F2514-14141000C WaterAnywhere

Are these vessels appropriate for the intended use?

Also, I found these membranes that appear to only need much lower pressure, which means you could use a much lower pressure pump I suppose... why don't people use these membranes?

2.5"- 14" Extra Low Energy RO Membrane, 190 GPD - M-T2514AXLE WaterAnywhere

Thanks...

- z

If you are going through the trouble of pressurizing salt water to 800 PSI, you should find a way to put at least one 40" membrane. Unless you are using a clark pump, you are going to be wasting a lot of energy. I found plenty of space under lazarette to put two 40" Pressure vessels, and C&C38 is more of a racer than a cruiser.