Unpickling Long Disused Watermaker

[Dockhead]

Originally Posted by contrail

Low pressure will affect quality and PPM. Guessing the pressure is an interesting notion! Based on what?

Based on flow. I opened the service valve and adjusted the pressure until the flow seemed about right. As low as possible whilst still giving a decent flow.

That's of course an invalid approach, but it's all I had at sea with no working gauge. I did manage to make a half tank of water.

[Dockhead]

So we got it apart and I found the gauge. I also found chemicals. We seem to be in business!

I'm a little nervous, however, about all that pressure. Do I put the fittings back together with sealant? Or not?

[poiu]

Originally Posted by Dockhead

So we got it apart and I found the gauge. I also found chemicals. We seem to be in business!

I'm a little nervous, however, about all that pressure. Do I put the fittings back together with sealant? Or not?

Well done on parts.

No sealant needed I expect. You have for sure O ring fittings, olive compression fittings, tapered thread fittings, cone fittings. None that require sealant to my recollection or anything else other than the tapered one, or maybe unsealed BSP ones, both of which needs ptfe, but yours maybe different. Not as far as I can see from the picture though.

Re pressure, it is pretty high. You should keep an eye on fitting tightness, especially the pressure side, to make sure they haven’t worked loose. Check each one. There will be a stress inducing bang, followed by a nasty salt water mess if they do. (Learnt the hard way).

[carstenb]

Originally Posted by Dockhead

So we got it apart and I found the gauge. I also found chemicals. We seem to be in business!

I'm a little nervous, however, about all that pressure. Do I put the fittings back together with sealant? Or not?

a little bit of teflon tape should be all that you need for fittings. Unless they are flared type that are metal to metal. There you should not need anything for the metal to metal flare.

[Dockhead]

Originally Posted by carstenb

a little bit of teflon tape should be all that you need for fittings. Unless they are flared type that are metal to metal. There you should not need anything for the metal to metal flare.

Even at that pressure?

[carstenb]

Originally Posted by Dockhead

Even at that pressure?

Metal to metal flare (note I wrote flare) fittings are designed for high pressure

[poiu]

Originally Posted by Dockhead

Even at that pressure?

Cone fittings work at much higher pressures. Maybe double.

[Dockhead]

We did a short sea trial today to verify the new gauge and installation. Success!! Doesn't leak a drop. The bad news is that at the correct pressure, production is low.

I think I'll try an acid wash. If that doesn't work, I'll change the membranes (which I have on board).

Thanks guys for all the good advice.

[mstr_cmdr]

You have reported a reduced product rate. I am sure you would be aware that product rate is affected by intake water temperature.
As an example, most RO water makers' specifications are predicated on a sea water temp of 25C (unless otherwise stated in the specifications sheet).
A seawater temp of 30C, will increase rate by ~25%; conversely a sea water temp of 10C, will reduce the product rate by up to 50%.
Have you calculated the product flow output with temperature compensation?
Also, what is the size of your membranes?
From the original pix, they look like (SW) 25-21 (where SW = salt water; 25 = 2.5in diameter of membrane; 21 = 21in length of membrane).
Another question: after conducting sea-trails with the RO water maker (operating time at nominal pressure not stated), what was the TDM reading after start; and prior to de-pressurising vessel and shut-down?
Cheers

[Tellie]

Originally Posted by poiu

Cone fittings work at much higher pressures. Maybe double.

Correct. Never use Teflon tape on these fittings, it only gets in the way of proper seating of the ferrule. These are hydraulic ferrule fittings that are designed to see far more pressures than any watermaker will produce. If these fittings are leaking there is only two reasons, 1) They are not secured tight enough or 2) There is crevice corrosion on either the ferrule itself or the fitting where the ferrule seats.

[Tellie]

Originally Posted by Marathon1150

The Spectra Ventura manual indicates that anything under 750 PPM is acceptable (see link below). The WHO recommends 300 PPM or better. We have a Ventura and it normally produces 200 PPM or better but did not when first commissioned. It was usually above 300 but an email exchange with Spectra indicated that we should keep using the machine and that water quality would improve and it did.

There are certainly many parts of the world where water is made by not well maintained watermakers for public consumption. It usually tastes salty and those who can afford it, buy bottled water rather than use tap water which is questionable for other reasons as well.

Spectra manual: https://www.spectrawatermakers.com/d...l-ae042616.pdf

The Spectra systems will shut down in high salinity at 748 ppms. Anything under 500ppms is what we are looking for. The manual is a bit misleading. Tech Geeks writing them

[Dockhead]

Well, we've arrived in Cabo Verde after another 5 days at sea.

We made a lot of water along the way. I decided on the following strategy -- the port side 700 liter tank was untouched and unused, left full of water from Las Palmas.

The stb tank was drawn down and then replenished with the watermaker.
The production is good -- apparently about 100l/h, but I'm somewhat concerned about TDS, which continues around 750. You can taste it a bit.

We have spare membranes on board and I thought maybe to change them out, but our engineer thinks it's a bad idea -- if we break something taking it apart, we won't get parts before our crossing.

I'm thinking this is not a dumb thought. So maybe we just keep it going like this, use the stb tank, and drink from 5l jugs we have aboard. When the 5l jugs run out, then we change over to the reserve tank and fill from there. We have 700l in the reserve tank.

Or maybe I'm overcomplicating it and 750ppm is not a big deal and we should just drink it and not worry about it.

What sayest ye?

[carstenb]

Originally Posted by Dockhead

Well, we've arrived in Cabo Verde after another 5 days at sea.

We made a lot of water along the way. I decided on the following strategy -- the port side 700 liter tank was untouched and unused, left full of water from Las Palmas.

The stb tank was drawn down and then replenished with the watermaker.
The production is good -- apparently about 100l/h, but I'm somewhat concerned about TDS, which continues around 750. You can taste it a bit.

We have spare membranes on board and I thought maybe to change them out, but our engineer thinks it's a bad idea -- if we break something taking it apart, we won't get parts before our crossing.

I'm thinking this is not a dumb thought. So maybe we just keep it going like this, use the stb tank, and drink from 5l jugs we have aboard. When the 5l jugs run out, then we change over to the reserve tank and fill from there. We have 700l in the reserve tank.

Or maybe I'm overcomplicating it and 750ppm is not a big deal and we should just drink it and not worry about it.

What sayest ye?

Changing the membrane should not be an issue. The end cap should screw off by hand or with very little effort. I’d do it but then I am a man and like most don’t read the instructions until afterwards……………

[poiu]

Originally Posted by Dockhead

Well, we've arrived in Cabo Verde after another 5 days at sea.

We made a lot of water along the way. I decided on the following strategy -- the port side 700 liter tank was untouched and unused, left full of water from Las Palmas.

The stb tank was drawn down and then replenished with the watermaker.
The production is good -- apparently about 100l/h, but I'm somewhat concerned about TDS, which continues around 750. You can taste it a bit.

We have spare membranes on board and I thought maybe to change them out, but our engineer thinks it's a bad idea -- if we break something taking it apart, we won't get parts before our crossing.

I'm thinking this is not a dumb thought. So maybe we just keep it going like this, use the stb tank, and drink from 5l jugs we have aboard. When the 5l jugs run out, then we change over to the reserve tank and fill from there. We have 700l in the reserve tank.

Or maybe I'm overcomplicating it and 750ppm is not a big deal and we should just drink it and not worry about it.

What sayest ye?

If you do the maths, the extra TDS in your water above the recommended 500 level is about equivalent to a gram if you consume 4 litres a day. If you put an extra gram of salt (1/6 of a teaspoon) in your cooking daily you wouldn’t probably notice. The WHO say we eat 9-12g of salt per day, but should eat under 5g, so the extra is not disproportionate and you could compensate.

[mvmojo]

Swapping out membranes should not cause any problems. Open the end of the pressure vessel, pull out the old membrane, slide in the new one, smear a little silicone on the o-ring if you have it and replace the end cap. Nothing to it. If you're not comfortable doing that you might want to question whether you're really prepared for a crossing. Most likely there will be more difficult problems to solve as you go!

In terms of the TDS, most of the literature state that anything under 1000 ppm is acceptable whereas under 500 ppm is desirable. But, these numbers are based on long term consumption. (FWIW, In my experience, anything under 300 ppm and you can't taste any salt.) Healthwise, you'll be OK at the 750 range you're getting. As poiu said, it's about like adding a pinch of salt to your food.