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Auto shut off valve question


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So I want to install an auto shut off valve to stop my tank overfilling once it’s done, I’ve ordered the same one a friend has but it hasn’t come yet. I looked up how this would work and thought it would be ok but when I was on the phone to Doug ordering my ro system he mentioned they aren’t good because it doesn’t shut off the waste and will damage the membranes. As far as I can see, the valve will connect between the prefilters and the ro membrane and then on the pure water line to the tank after the membrane. So when the tank gets full the pressure will cause the valve to shut off the water before the membrane right? I’m not getting the problem at the minute so if anyone can enlighten me I’d be very grateful! I didn’t want to bother Doug yet with all my questions, mans got a business to run! So thought I’d check for advice here first.

 

Edit: thought it might be helpful to post a link to the one I’ve bought to show what I’m talking about. https://www.ebay.co.uk/itm/273412698037

Edited by Purejb
Add link to valve I mentioned
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I believe that the device may be best to install on the pipe that connects to the prefilters from your water main and the pure out line. That way when the pressure rises in the pure to tank line it shuts off the whole supply to the pre and ro. That way there is no water going into the ro but the pressure on the ro out (Pure line) will be maintained by the float valve. Well that's my understanding anyway. Doug will be correct so just keep checking your tds out to make sure RO isn't failing, I am guessing its 450gpd or under? If so then a new RO isn't that expensive. If it's a 4040 or a 2040 then I wouldn't use one of those devices!!!!

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Purefreedom use a float switch with a 12v solenoid valve. When the tank is full the float switch cuts power to the solenoid valve. The solenoid valve is situated on PF van mount system between the prefilters and the r/o membrane. Always best to use an r/o that has a good production output. The majority of van mounts are 4040's. Some with a smaller tank use 4021 r/os.

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22 minutes ago, spruce said:

The solenoid valve is situated on PF van mount system between the prefilters and the r/o membrane.

Any idea why the put the solenoid valve between pre filters and RO? I would have thought it's best to put it between the supply and the pre filters? Just trying to understand why both Doug and PF say it's between pre filters and RO.

Edited by ched999uk
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Well for the valve i bought it's 1/4" holes so I imagine that's why it fits there, and unless I'm missing something seems that it will work and also not require solenoid or power supply. That's why that way appealed to me. Just wanted to check i hadn't overlooked something though

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1 hour ago, ched999uk said:

Any idea why the put the solenoid valve between pre filters and RO? I would have thought it's best to put it between the supply and the pre filters? Just trying to understand why both Doug and PF say it's between pre filters and RO.

I guess the answer is that the prefilters have removed any grit from the water that could get trapped in the valve seat on closing. 

My solenoid valve is before the prefilters and at times our water has been laden with sediment. In the 14 years I've had the system in operation I have never had an issue. However, if I was a supplier I would advise the best option which would be between the prefilters and r/o. This is purely because of grit on the valve seat. The majority of us will obtain water from the local water board. But there may be some, one I know of in Scotland, who takes water from a mountain stream and purifies it for drinking with an ultraviolet light. That water might have some larger pieces of grit in it from time to time. The trap is a crude box upstream and water gravity fed to the house.

Edited by spruce
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13 hours ago, spruce said:

I guess the answer is that the prefilters have removed any grit from the water that could get trapped in the valve seat on closing. 

My solenoid valve is before the prefilters and at times our water has been laden with sediment. In the 14 years I've had the system in operation I have never had an issue.

I run mine this way too. I figured there would always a be a constant flow of water, albeit slow, through the pre filters. I imagine this would lower the lifespan on the filters? My thinking is that the tap it’s connected to doesn’t stop attempting to flow once the solenoid kicks in? Having said that my solenoid is now fitted beyond the water meter I fitted and this doesn’t increase when the solenoid kicks in so there certainly isn’t a full flow of water the same as when the solenoid is open.

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1 hour ago, P4dstar said:

I run mine this way too. I figured there would always a be a constant flow of water, albeit slow, through the pre filters. I imagine this would lower the lifespan on the filters? My thinking is that the tap it’s connected to doesn’t stop attempting to flow once the solenoid kicks in? Having said that my solenoid is now fitted beyond the water meter I fitted and this doesn’t increase when the solenoid kicks in so there certainly isn’t a full flow of water the same as when the solenoid is open.

My IBC tank is in the back of my garage. Just to make sure the inside of the garage didn't get flooded out if the solenoid valve didn't close fully, I fitted an overflow pipe to the drain outside.

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6 hours ago, spruce said:

My IBC tank is in the back of my garage. Just to make sure the inside of the garage didn't get flooded out if the solenoid valve didn't close fully, I fitted an overflow pipe to the drain outside.

I did the same but on one occasion it still overflowed in the garage. I have a 1/4" pipe processing into the tank. The booster pump is controlled to switch off by a float valve. The water then just trickles in under 20 psi mains pressure. A few inches higher and another float valve is supposed to stop the flow entirely. It doesn't stop it fully but reduces it to the slowest trickle. A few inches above this level I have a 3/8" overflow with around 8 ft of pipe to the outside of the front door of the garage, so I can spot any overflow on the drive. I thought it would all work perfectly. It used to sometimes go a couple of inches above the overflow and then start running out of it. However on one occasion the level rose until it overflowed out the lid. I think what happened was that the surface tension at the overflow was too strong for the water to break through even though there are no high spots in the pipe to trap air.

Lesson learned : I knew the overflow should always be larger than the inlet but if I were doing it again I'd go at least 1/2" or 3/4".

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1 hour ago, Davy G said:

I did the same but on one occasion it still overflowed in the garage. I have a 1/4" pipe processing into the tank. The booster pump is controlled to switch off by a float valve. The water then just trickles in under 20 psi mains pressure. A few inches higher and another float valve is supposed to stop the flow entirely. It doesn't stop it fully but reduces it to the slowest trickle. A few inches above this level I have a 3/8" overflow with around 8 ft of pipe to the outside of the front door of the garage, so I can spot any overflow on the drive. I thought it would all work perfectly. It used to sometimes go a couple of inches above the overflow and then start running out of it. However on one occasion the level rose until it overflowed out the lid. I think what happened was that the surface tension at the overflow was too strong for the water to break through even though there are no high spots in the pipe to trap air.

Lesson learned : I knew the overflow should always be larger than the inlet but if I were doing it again I'd go at least 1/2" or 3/4".

I have a 4040 and I produce about 2lpm of pure. A 1/2" length of garden hose is more than enough to keep up with the overflow rate. I've tested it. However, if I had a booster pump then production would be more. I'm not sure if my 1/2" hose would suffice then.

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1 hour ago, spruce said:

I have a 4040 and I produce about 2lpm of pure. A 1/2" length of garden hose is more than enough to keep up with the overflow rate. I've tested it. However, if I had a booster pump then production would be more. I'm not sure if my 1/2" hose would suffice then.

In my case the 3/8"overflow pipe was plenty big in itself. I only produce one to one and a half litres a minute. I had tested it on several occasions and It had worked the finest until the one occasion when it didn't during an overnight processing. Subsequently for a test I started the flow by a gentle suck on the open end and it was down to the correct level in a very quick time.

The problem was that on the one occasion it overflowed the water for some reason was not able to break the surface tension at the overflow outlet to allow the outflow to start. I'm pretty sure if I'd had 1/2" or bigger there wouldn't have been a problem.

Edited by Davy G
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9 hours ago, Davy G said:

In my case the 3/8"overflow pipe was plenty big in itself. I only produce one to one and a half litres a minute. I had tested it on several occasions and It had worked the finest until the one occasion when it didn't during an overnight processing. Subsequently for a test I started the flow by a gentle suck on the open end and it was down to the correct level in a very quick time.

The problem was that on the one occasion it overflowed the water for some reason was not able to break the surface tension at the overflow outlet to allow the outflow to start. I'm pretty sure if I'd had 1/2" or bigger there wouldn't have been a problem.

I have an on/off tap on my system that allows me to drain the tank. Its connected with 1/2" hose. The tap is also used now and again to fill a 25 litre plastic container. If the tank is low and there isn't water in the connecting hose, opening the tap doesn't always allow water to flow even although the tops of the coiled hose are below the water level in the tank. If the tank is full that container fills pretty fast.

 

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18 minutes ago, spruce said:

I have an on/off tap on my system that allows me to drain the tank. Its connected with 1/2" hose. The tap is also used now and again to fill a 25 litre plastic container. If the tank is low and there isn't water in the connecting hose, opening the tap doesn't always allow water to flow even although the tops of the coiled hose are below the water level in the tank. If the tank is full that container fills pretty fast.

 

Yeah, I think if there was unrestricted height capacity for the water above my overflow outlet, eventually the weight of the water would have been enough to start the flow. Trouble is the lid is only about 3 or 4 inches above the overflow.

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