Watermaker and generator on same thru hull

[mvmojo]

Originally Posted by SV THIRD DAY

DANGER....BAD BAD ADVICE....

There are so many bad things that can happen with this set-up I'm not going to get into them on Good Friday....but PLEASE don't do something like this unless you like drama and spending money on costly and needless repairs.

This is one of those "I read it on the internet" fiascos....

Please enumerate, we're all hear to learn and share our knowledge and experience. This is not a fiasco at all, and not something "I read on the internet"... it was the plumbing method recommended by my watermaker manufacturer. I used it an hour per day for 6 years in the Caribbean with no problems what-so-ever - made tens of thousands of gallons of water! As long as the output of the generator water pump">raw water pump is greater than the cooling needs of the genset engine, what sort of "drama" and "bad things" can happen that would be avoided by having a separate thru hull and separate boost pump? Please educate me by providing more detail.

[rthompsona]

Thank you for all of the good ideas.

Based on the feedback, I am leaning towards adding the second thru hull and strainer. I am planning a long trip, and don't want to experiment just before I leave.

I am set up with the generator and watermaker on the port side. The only other thru hull I could consider working with would be in the starboard hull, and there is no easy way to get there.

I think it will not be too hard if I place the new thru hull on the inboard side of the port hull. The generator thru hull is on the outboard side. My only concern is that I will be about 10 inches in front of my speed transducer. It will also be about 8 inches further down into the keel. Does anyone have experience with a thru hull that close to a speed transducer. Do you think it will produce a vortex that will mess up the pinwheel?

[BobFord]

I have a set up like you describe - 12mm inlet to feed w/maker and Genny.

Problems-the inlet works to capacity all the time.
- a minor blockage , piece of grass ,causes the lift pump to suck air which the w/maker dosen't like.

Next slipping i'll be installing a second inlet to a separate, dedicated sea chest.

[Quadrille in JB]

Your water maker will be much happier with its own thru Hull. On both of my sailboats the engine thru Hull was only 1/2” and both engines ran hot when pushed hard. I added a new 3/4” thru Hull and strainer for the main engines and used the original 1/2”thru hulls for the WM. The engines run cool and the water maker is happy with its own dedicated thru hull.

[Reefmagnet]

I put a dedicated through hull in my boat when I installed the watermaker. The other option is to use a manifold, but in your case that is probably more effort than reward. When adding the extra through hull, you can place it in an optimal position. Not just in regard to the watermaker plumbing, but in regard to other outlets. You need to avoid any possibility that the the intake can suck in discharges, especially oil and chlorine, from adjacent outlets. when the watermaker is in operation because these things will damage the membrane in short order. Oh yeah, probably want to avoid sucking in grey and black water also!

[Pelagic]

Originally Posted by rthompsona

Thank you for all of the good ideas.

Based on the feedback, I am leaning towards adding the second thru hull and strainer. I am planning a long trip, and don't want to experiment just before I leave.

I am set up with the generator and watermaker on the port side. The only other thru hull I could consider working with would be in the starboard hull, and there is no easy way to get there.

I think it will not be too hard if I place the new thru hull on the inboard side of the port hull. The generator thru hull is on the outboard side. My only concern is that I will be about 10 inches in front of my speed transducer. It will also be about 8 inches further down into the keel. Does anyone have experience with a thru hull that close to a speed transducer. Do you think it will produce a vortex that will mess up the pinwheel?

I think your instincts are right!
Why compromise both, if you don't have to?

A thought, if there is space, you could plumb a crossover to supply both in case 1 thru hull /strainer gets blocked at an inopportune time.

When I first bought my boat the Main Engine, Water maker and large AC compressor was connected to same thru hull.

You could not run all 3 at same time. So I added a 2nd "larger" thru hull and strainer to supply RO & AC with a back up for Main Engine

[HankOnthewater]

Originally Posted by Lodesman

I think the real answer depends on the water demands of the two devices, and whether or not the thru-hull is large enough to achieve the flow-rate required. If you can't figure out the answers to those three things, then go with another thru-hull; as others have said that could paired with a low-use device such as an head inlet.

I think Lodesman is right, and a large enough intake should be OK to use the same inlet fitting. But what is large enough?

Can anyone tell how much seawater a (for argument's sake) 25 gallon (100 lt) per hour watermaker uses? Or is there an approx. formula ie for every gallon of fresh water made per hour, 'xy' gallon of seawater is needed?

Can anyone tell how much seawater a (for argument's sake) a 25 HP engine (ie genset) and a 100 HP (main) engine use for cooling? Yes I know, how long is a ball of string, but ball park figures would be nice to know or vital to know PRIOR to sharing a through-hull I would think.

Knowing both the above (eh, the figures for the engine(s) and the watermaker on your boat), THEN one can make an informed decision whether to share the same inlet or not.

......On further thought, what about some boats that have one single seawater inlet (standpipe), that are often 1.5" or 40 mm in diameter with a very large capacity filter?

[deluxe68]

Dumb question. What is the difference between a t-connector and a hard-y? Why would the t connector be more apt to get air bubbles?

[Lodesman]

Originally Posted by mvmojo

As long as the output of the generator raw water pump is greater than the cooling needs of the genset engine, what sort of "drama" and "bad things" can happen that would be avoided by having a separate thru hull and separate boost pump?

Not speaking for Rich, but I see a couple of issues. First Dow Filmtech membranes have a maximum operating temperature of 113ºF (40ºC) - taking tropical water and running it through a hot engine might put you close or over that mark. I doubt an engine's heat exchanger is built to be foodsafe; running your feed water through it runs the risk of picking up heavy metals; and if there's a tube leak, you could get anti-freeze (the poisonous variety) in your water. I don't know if these will make it through the membrane or have an adverse effect on the membrane, but I would prefer to avoid the issue altogether. The final issue, is that water that should be cooling your exhaust is diverted, possibly leading to exhaust components getting too much heat.