DIY Watermaker

[foggysail]

Originally Posted by Stillraining

Put an "unloader" on the pressure side...basically a pressure relief valve...any restriction causing pressures to rise above its set limits allows a dump or "unload" of partial flow...All good pressure washers have them..its what protects the pump when you release the trigger on the gun....they are self resetting and designed to have flow through them pretty much constantly.

Yes, right on! I sort of screwed up by not quoting the post I was responding to.

But since you mentioned an unloader, I have a couple of questions anyway. In a previous post in this thread, someone else (you??) mentioned using an inexpensive pressure relief valve from a pressure washer. I did give that some thought but I am not sure that will replace a pressure regulator such as the CAT 7070 which is in the $240 range.

Heck, I could be wrong as I thought/think a pressure relief valve is just that, a device that will relieve excessive pressure. But using something like that might not give pressure consistency needed to properly force liquid through a membrane. Any ideas?

Foggy

[beau]

The problem is here in Australia, i was quoted $800. for a CAT pressure valve. Lucky for me the saleman found me an equivalent valve, for $170.00 I will let you know if there are problems (it is USA manufactured)

[foggysail]

Originally Posted by beau

The problem is here in Australia, i was quoted $800. for a CAT pressure valve. Lucky for me the saleman found me an equivalent valve, for $170.00 I will let you know if there are problems (it is USA manufactured)

Thanks Beau!! Also gave you a "THANKS!" After over 500 posts without a green lighted square---- you deserved to have it lighted!!!!

Foggy

[beau]

I don't understand about the "green" lighted square, could you explain

[beau]

The other thing I forgot to mention, the salesman at this quality pressure washer distributor also told me he could replace the plungers on my "cheap" ebay pressure washer with ceramic ones.
Also a spare brass pump was only $150.00 (ebay)

[foggysail]

Originally Posted by beau

I don't understand about the "green" lighted square, could you explain

It is the one that says "you will receive many thanks" when you click on it but seems to remain not lighted until you get at least one. I think thats it.

Good news on the plungers if they don't offset the lower cost pump price.

[goboatingnow]

There's allways greAt confusion over valve types

On the pump there may be an " unloader" valve which is the same as a pressure relief valve. Both are set to prevent overpressure damaging things.

The actual working pressure typically 800 psi for SWRO , is set by a " back pressure" valve this is placed at the end of the pressure run. It's a normally closed valves with a spring controlled opening. A pressure regulator is a normally open type of valve placed early in the high pressure feed and is a different device

RO systems usually use a back pressure valve. They are widely available once you know what to look for . Equally for fairly constant flow a simple " needle " valve will also work but will allow the back pressure to vary if the flow rates vary. But in say fixed speed pump systems they work fine and are much cheaper.

By the way has anyone built up any reliability data on brass pumps heads. Be interested to see how long they last.

Dave

[Stillraining]

Originally Posted by foggysail

Yes, right on! I sort of screwed up by not quoting the post I was responding to.

But since you mentioned an unloader, I have a couple of questions anyway. In a previous post in this thread, someone else (you??) mentioned using an inexpensive pressure relief valve from a pressure washer. I did give that some thought but I am not sure that will replace a pressure regulator such as the CAT 7070 which is in the $240 range.

Heck, I could be wrong as I thought/think a pressure relief valve is just that, a device that will relieve excessive pressure. But using something like that might not give pressure consistency needed to properly force liquid through a membrane. Any ideas?

Foggy

Im sure you could adjust the dump setting about anywhere you want within the valves capacity....Mine is adjustable but I have no pressure gauge on my washer so I can not tell you what the actual line pressure is when the trigger is pulled on the gun compared to what presser it takes to open the relief valve...But I have to think that if my pump is putting out 1800 PSI ( I was wrong about the 1500 I just looked it up)...My pea brain tell me the back pressure or line preasure created from the tip in the end of the gun must be producing about 1/2 restriction so there is your 800 psi right there....and thats going to be at the rated 4.0 GPM

A simple test or 3 with a gauge installed in line would allow you to adjust the unloader to within 100 PSI I would think of that preasure...any additional preasure would leak by the valve once reached its desired setting....Here again, and this is important...an Unloader is not a fully open or closed valve like a pop off valve on a air tank or hot water heater...it is a spring loaded regulator basically only open...sensing as little or as much as needed to maintain protection of the pump...I don't see where you would need two valves..a good unloader will serve both purposes mentioned.

Im thinking your cat 70 70 valve is exactly what im talking about I will look it up.

[foggysail]

Originally Posted by goboatingnow

There's allways greAt confusion over valve types

On the pump there may be an " unloader" valve which is the same as a pressure relief valve. Both are set to prevent overpressure damaging things.

The actual working pressure typically 800 psi for SWRO , is set by a " back pressure" valve this is placed at the end of the pressure run. It's a normally closed valves with a spring controlled opening. A pressure regulator is a normally open type of valve placed early in the high pressure feed and is a different device

RO systems usually use a back pressure valve. They are widely available once you know what to look for . Equally for fairly constant flow a simple " needle " valve will also work but will allow the back pressure to vary if the flow rates vary. But in say fixed speed pump systems they work fine and are much cheaper.

By the way has anyone built up any reliability data on brass pumps heads. Be interested to see how long they last.

Dave

Dave-- there is discussing here in this thread about brass pumps. Appears they will last for years...........IF THEY ARE PURGED of salt water after use and after pickling. I purchased a brass pump along with a 2HP motor.

Foggy

[foggysail]

Stillraining--

Thanks--

[Stillraining]

Yep I just looked up your 7070 valve...regulator/Unloader...one in the same..different name for the same thing....yes they are spendy...but you NEED the protection...and I can say this with out much risk...they never wear out at least with fresh water use...mines 20 years old.....Mine is a differnt brand though and all brass

[Brent Swain]

My brass relief valve, new at a pressure washer place , cost me $35. It's a spring holding a ball in a hole adjusted with a fine thread bolt. The bolt was mild steel, which I replaced with stainless. You could easily build your own.

[Yachts66]

Help de-confuse me please. It was my understanding that for the system to work efficiently one needed a pressure gauge and a needle valve to control the pressure. The reason being as the temperature and salinity changes so does the required pressure in order to optimize the system. If you are running the pump at a higher pressure than is necessary you are wasting energy and also may risk damaging the membranes.

After reading the posts above some seem to think such things as pressure gauges superfluous. So....what's the the expert's opinion here?

Thanks,

Thomas

[osirissail]

Originally Posted by Yachts66

Help de-confuse me please. It was my understanding that for the system to work efficiently one needed a pressure gauge and a needle valve to control the pressure. The reason being as the temperature and salinity changes so does the required pressure in order to optimize the system. If you are running the pump at a higher pressure than is necessary you are wasting energy and also may risk damaging the membranes.
After reading the posts above some seem to think such things as pressure gauges superfluous. So....what's the the expert's opinion here?
Thanks, Thomas

Yes and No. There are many commercially made R.O. watermakers that do not have high pressure or any other guage. The high pressure regulator valve has been set at the factory for 800psi which is the normal operating pressure for sea water R.O. The more expensive machines include all sorts of guages, flow meters, and salinity testers built in along with other "bells and whistles."
- - Once you have tested and set and locked the mechanical high pressure regulator for 800 psi, the guage is superfluous. However, if you move to a fresh water or brackish water area then you must reset the regulator.

[Tellie]

Originally Posted by Yachts66

Help de-confuse me please. It was my understanding that for the system to work efficiently one needed a pressure gauge and a needle valve to control the pressure. The reason being as the temperature and salinity changes so does the required pressure in order to optimize the system. If you are running the pump at a higher pressure than is necessary you are wasting energy and also may risk damaging the membranes.

After reading the posts above some seem to think such things as pressure gauges superfluous. So....what's the the expert's opinion here?

Thanks,

Thomas

A pressure gauge is not superfluous. It is rather essential. Operating pressures on water makers especially plunger driven types can easily exceed rated pressures. As you state, salinity and water temperatures play important roles in pressures created within a membrane vessel. Setting a pressure regulator and forgetting it has led to more than one water maker with ruined membranes, cheap vessels split, cheap hoses and fitting failures. Especially if you cruise into different climates. So yes, the relativly small cost of a good pressure gauge is worth the insurance as well as being able to tell what's happening with your water maker and whether it is amiss or working properly.