Re: [Amel Yacht Owners] Dessalator Water Maker Issues & New Photos

Steve Constantine <maramu_49@...>


I may have a possible answer to your question about the higher EC reading when the pressure is below the green range.

According to Rod Boreham, the membranes are not perfectly cylindrical. They have a slightly larger diameter in the center than at the two ends. The reason for this is to allow for distortion when the pressure is applied.

The membranes are not constructed by rolling a square sheet of material from one side to the other. They are rolled corner to corner. This creates angular seams along the length of the tube. They are actually rolled with enough slack to account for a perfect fit under pressure. If you run the water maker below the prescribed pressure, you are squeezing salt water past the unsealed seams. In other words, they have to be fully pressurized to seal properly. The good news is that your EC appears to be finding it.

Rod was quite emphatic that the Dessalator should only be operated entirely within the green zone. Any higher or lower will result in problems. You should check with Rod to be sure though. I think I interpretted his recommendations correctly, but one never knows.

It may also be due to something else entirely, but this seemed to make sense to me.


Steve and Donna. SM#340 Summer Love

amelliahona <> wrote:
--- In, eric <kimberlite@...> wrote:
24 Feb 2006

I purchased 3/8 inch quick connect fittings at Home Depot (white plastic, push together
fitting that are good to 100 psi) and cut the blue 10 mm product water line. There is
virtually no pressure on this line . The sensor for the EC system that I mentioned
previously plumbs into a 1/2 in pipe thread fitting. I bought a 1/2 inch PVC pipe "T"
fitting, and plumbed it with the quick connects. So the sensor is just immersed in the
product water as it flows by. I'll post photos after my next trip. I took 220 volt 50 Hertz
Power from the circuit breaker for the water maker.

I have noticed that upon startup the EC briefly goes to somewhere above 2000
microsiemens but then within 30 seconds it comes down to about 350. If you run the
watermaker below green range pressure the EC is actually higher than if run in the normal
operating range. I don't quite understand that but it is consistent. I inquired of the Wafer
Fire and Ice people that I bought my membranes from and they tell me that this is normal.
They call it TDS creep. Evidently when the system is shut down the high TDS on the sea
water side draws the product water back across the membrane by osmotic pressure. This
then concentrates the solulte in the product water side as more and more water is drawn
back across the membranes. The longer the system sits idle the more TDS creep there is.
So the initial minute or two of product water will be high in TDS (EC). Perhaps that is why
the Dessalator system had a timer. I have spent hours corresponding with Dessalator and
they will not provide me with schematics or a logic diagram for the system. I plan to take
detail digital photos of the circuit boards next month when I get on the boat and reverse
engineer the electronics. It doesn't appear to be that complicated. Dessalator says that
they do have spare logic circuit boards for sale and will install one if I ship my system to
them but they at the same time make no guarantees that the system will behave as
advertised even with a new board installed. This is about the goofiest company policy that
I have ever run across.

Regards, Gary

How did you hook the salinity sensor into the watermaker output?
Fair Winds,
Amel Super Maramu #376 Kimberlite

Sailing Sailing yacht Amel Boating sailing


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