Watermaker Product flow pressure

[Tellie]

[QUOTE=Nauticatarcher;2151377]


"just because most watermaker installations feed into the top of tanks is probably due to the fact that that is the easiest place to do it,"

"any way I'm big enough and ugly enough to make my own decisions, thanks for all the advice."

With all due respect. You asked for advice and you were given advice. But in the end it is certainly your boat to do with as you please.

[Nauticatarcher]

With all due respect. You asked for advice and you were given advice. But in the end it is certainly your boat to do with as you please.[/QUOTE]

Actually I didnt ask for advice, I asked if anybody knew the pressure of the product waterflow of a specific RO membrane operating at a specific pressure. what I got was a lot of advice, Thanks anyway

[sailcrazy]

FWIW....when I installed our watermaker I connected the product water line to the deck fill tube. When I make water, the made water flows from the watermaker to the deck fill line and then into each of my 4 tanks, just as if I was filling with a hose at the deck fill, all via gravity. The vent lines remain as vent lines, and I don't mess with the tank suction line (possibly inducing a suction leak. So far(1+year)...it has worked perfectly.

[jamhass]

The reason WM manufacturers recommend a separate fitting in the top of the tank is then the product enters the tank with a "free surface" thus disconnecting the membrane hydraulically from the rest of the water system -- unless of course you overfill the tanks so there is no free surface.

Installed this way ensures that the back pressure on the membrane is limited to the head difference between the membrane and the product delivery point. You can ignore any elevation change in the tube run itself, it is only the net elevation difference that counts -- as long as the exit is a free surface.

[Nauticatarcher]

"Installed this way ensures that the back pressure on the membrane is limited to the head difference between the membrane and the product delivery point. You can ignore any elevation change in the tube run itself, it is only the net elevation difference that counts -- as long as the exit is a free surface.[/QUOTE]

the back pressure on the membrane (which is below tank level) from putting product water into bottom of tank will be less than putting it into the top of the tank until the tank is full as pressure will slowly increase as tank fills, as our system will have a three way NC closed solenoid valve in product line close to the membrane when watermaker is not working back pressure will be virtually nil and while operating less than placing it to tank top so I really cant see any issues with doing this, that is unless my understanding of fluid dynamics is completely wrong

[svlamorocha]

Originally Posted by Nauticatarcher

watermaker outlet has a TDS controlled normally closed three way solenoid so in the event of any contamination it will close and isolate watermaker from FW tanks, back pressure is well within membrane spec's so I really cant see any reason why not too do this.

Those who make a living out of designing drinking water systems have learned not to rely on valves that might fail when you can rely on the atmosphere to isolate a tank that might be contaminated.


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[svlamorocha]

Originally Posted by jamhass

The reason WM manufacturers recommend a separate fitting in the top of the tank is then the product enters the tank with a "free surface" thus disconnecting the membrane hydraulically from the rest of the water system -- unless of course you overfill the tanks so there is no free surface.

Installed this way ensures that the back pressure on the membrane is limited to the head difference between the membrane and the product delivery point. You can ignore any elevation change in the tube run itself, it is only the net elevation difference that counts -- as long as the exit is a free surface.

+1. Free surface works all the time.

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[SV THIRD DAY]

Originally Posted by Tellie

All watermaker product lines (The the lines that supply fresh water made from your system) should lead to the top of each tank, not the bottom or a manifold located below the fresh water tank/s.

Exactly Right....ignore good advice from experts in the field at your own peril. Just because I have seen this disaster before, doesn't mean it could happen to you of course...you could have a magic boat where things don't go wrong.

Originally Posted by Nauticatarcher

our system will have a three way NC closed solenoid valve in product line close to the membrane when watermaker is not working back pressure will be virtually nil and while operating less than placing it to tank top so I really cant see any issues with doing this, that is unless my understanding of fluid dynamics is completely wrong

Such an installation set-up would not be allowed on our water makers not because of head pressure, you are missing the issue that matters. What matters is that the first time your NC Solenoid either fails and snaps shut while making water OR you forget to open it...KA...BOOM...where do you least want water spraying because it WILL blow apart the low product water tubing and spray where you want it least. Been there...seen that on multiple boats. This is why in our water maker manual in big Bold Red Print says that the product water line can NEVER be blocked and if you want to put a 3-way valve in to direct the product water flow to different tanks, which is common, you need to use a non-blocking transitioning 3-way valve. Why...because I have seen normal 3-way valves left in the "middle" or off position and Poop...spray..there goes you Autopilot or Refrigeration or inverter...I have seen it all.

The Water Maker experts on this forum give advice and recommendations based on thousand of installations, but there is always the guy who thinks he can find a better way that all the experts have just been too dumb to think about. Or perhaps the experts have tried it and seen disasters....??

[Nauticatarcher]

A normally closed three way solenoid valve, will never block waterflow as it will either be directing flow to tank or exhaust port, they are a very reliable valve and Ive never had one fail yet, it will also stop tank being contaminated if membrane fails as long as TDS controller is doing its job and even if controller fails it will place valve in overboard discharge mode, much more reliable than manual three way valve.

Just in case you dont know how a three way NC solenoid valve works
water flow is from inlet port to exhaust port until solenoid is energised then flow goes to outlet port, shuttle valve has spring return on it and even if it got stuck part way would split flow between valves , all wetted parts are 316SS

[TeddyDiver]

Originally Posted by Nauticatarcher

Just in case you dont know how a three way NC solenoid valve works

Go ahead, it's your boat.. Tellie and SV 3rd Day have seen only thousands of RO installations, what do they know...

By the way, how many you have done?

BR Teddy

[Nauticatarcher]

Originally Posted by TeddyDiver

Go ahead, it's your boat.. Tellie and SV 3rd Day have seen only thousands of RO installations, what do they know...

By the way, how many you have done?

BR Teddy

This is not my first installation, last one went into tank top and this one still may do, but as yet nobody has provided a reason why not to put product water in to tank water outlet that stands up, and sorry just because it always done that way or the manfacturer states that it must be done that way dont convince me it cant be done,
1) back pressure is inside membrane spec's in fact its less than putting it into tank top until tank is full (membrane below tank level scenario)
2) with three way solenoid valve tank is isolated from membrane when watermaker not in use and exhaust port on valve is open so no chance of blocking product water flow, any way with a TDS controller and 3-way solenoid valve it would make no difference if water went in to bottom of tank or top as far as blocking flow and a TDS controlled valve probably a hell of a lot more reliable than a manual valve and will also prevent contaminating tank in case of membrane failure

so apart from bowing down to the collective wisdom of the experts what am I missing ??

[sailorboy1]

I don't see any real pressure difference in a line going to the top of a water tank or to the bottom (i.e. into the pickup tube), either way the water column has to get to the top of the tank. It would seem to me that except for a case of a clog/closed valve, that the highest pressure in the line would be when the water tank is full and is overflowing.

To the OPs' question of max pressure on the outlet, I don't think it matters as long as it doesn't exceed the limits for the fittings and components. All the membrane cares about is the differential pressure across it.

[phorvati]

In my 12 years of running the DIY watermaker Ive had many revisions. Teed off of vents, deck fill hose, etc etc. But i have eventually arrived at a version that the pros suggest. I am using separate 3/8" tubing and have put a new fitting at the top of each tank, with an extra tubing that goes into galley sink for sampling, and testing, and an extra tubing that goes into 6 gal bladder tank used only for flushing.
Product back pressure will cause issues. Its kinda like clogged engine manifold.