Tank gauges and water maker

SanDiegoChip · #1 (**permalink**) 12-20-2010

At present we have some sight gauges that were made up by the PO. They seem to work good and are fine for at the dock fill ups because it does not take long. They are located below our salon deck as is our engine. This requires us leaving open a large hatch. We would not like to leave this hatch open for long periods of time every other day if we needed to using a water maker. It is heavy and it is a safety issue. We have never used a water maker but will be installing one next year.

We are considering installing water tank gauges. Because the tanks are stainless steel and we do not have the room or say the desire to drill in from the top we are thinking of side sensor gauges. They are pricey. To install them requires we cut some plywood from the side of the tanks. At this time we are re-powering so w we have the engine out for the next month or so. Now would be the time to do this job.
My question is with a water maker do you need water gauges.
We have two tanks with 55 gal in each one. So if say a water maker does 10 gal an hour would we realy need to worry about filling up the tanks if we ran it a couple hours every other day? Say we used more than that or keep track etc?
How does it work when you are using a water maker? Need to know how full the tank is or is there usually plenty of room?
Would we need to see the tank levels each time we make water or just check to see if the tanks have room?

JiffyLube · #2 (**permalink**) 12-22-2010

I thought about that same issue too. I plan to use one tank at a time, isolating one tank as it's being filled by the watermaker. When one tank is filled I'll switch over to the other one, and fill that one while using the just filled tank. I'll be able to tell when the tanks are full when they over flow the vent, just like what happens when I fill the tanks at the dock. After awhile of living off the tanks I should be able to estimate usage, at least good enough to satisfy me.

noelex77 · #3 (**permalink**) 12-22-2010

Just a word of caution. I understand watermaker membranes do not like back pressure in their product water outlet.
If you wait until the tank is overflowing, if the overflow is above the watermaker you may be risking damage.
I have no idea if this is a significant risk, but I would be careful (or check with the manufacturer) until someone with better knowledge of watermakers advices its OK.

JiffyLube · #4 (**permalink**) 12-23-2010

Quote:

Originally Posted by noelex77

Just a word of caution. I understand watermaker membranes do not like back pressure in their product water outlet.
If you wait until the tank is overflowing, if the overflow is above the watermaker you may be risking damage.
I have no idea if this is a significant risk, but I would be careful (or check with the manufacturer) until someone with better knowledge of watermakers advices its OK.

How much back pressure could there be filling up a vent line? I think once the vent line over flows I can switch the diverter valve for product water to the other tank, and shut the system down. Anyone see a problem with that?

noelex77 · #5 (**permalink**) 12-23-2010

Quote:

Originally Posted by JiffyLube

How much back pressure could there be filling up a vent line? I think once the vent line over flows I can switch the diverter valve for product water to the other tank, and shut the system down. Anyone see a problem with that?

If I remember correctly every foot of water is about 2psi. Even if this rough rule is right it doesn’t really help as I have no idea what back pressure in the product flow could lead to membrane damage, just that it can cause problems if “excessive”
I am sure with the vast knowledge of the forum someone will tell us the answer.

JiffyLube · #6 (**permalink**) 12-28-2010

Quote:

Originally Posted by noelex77

If I remember correctly every foot of water is about 2psi. Even if this rough rule is right it doesn’t really help as I have no idea what back pressure in the product flow could lead to membrane damage, just that it can cause problems if “excessive”
I am sure with the vast knowledge of the forum someone will tell us the answer.

Is that 2psi for every foot of water going up a 1/4" or 1/2" vent line?

noelex77 · #7 (**permalink**) 12-29-2010

Quote:

Originally Posted by JiffyLube

Is that 2psi for every foot of water going up a 1/4" or 1/2" vent line?

The pressure is not dependant on the size of the vent line only on the height of the water column above the membrane.

mitchbrown · #8 (**permalink**) 12-29-2010

Hi Group

Its not 2 psi. .455 Psi will lift water one foot.

Mitch

noelex77 · #9 (**permalink**) 12-29-2010

Quote:

Originally Posted by mitchbrown

Hi Group

Its not 2 psi. .455 Psi will lift water one foot.

Mitch

Thanks Mitch must have been 2 foot of water is about 1psi, not every 1 foot of water is about 2psi that I was trying to remember. Should have Googled it, but my internet from the boat is very slow at times.

CapnBilll · #10 (**permalink**) 12-29-2010

You can put a sight tube anywhere before the pressure pump, it doesn't have to be attached to the tank. If the level is really important I would consider putting in a float switch. Then you can wire it to turn off the watermaker.