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Thread: Cool Gadget for my Apex - TDS Meter

  1. #26
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    I may not understand what you're doing with the solenoid, but, typically they stop or allow flow(not reduce pressure/ this is what a pressure regulator is used for - google Watts P-60), pressure is the resistance to flow, so while closed you are correct there will not be pressure or flow toward the schedule 80 TEE you plan to put the probe in, however, when you command the solenoid to open, the water will flow through the solenoid and apply whatever pressure is available behind the solenoid to keep the flow. So.... assuming your solenoid closes before your float it will receive less pressure, IMHO not 1 PSI even with a float open, as 1/4" tube will provide substantial resistance (Pressure) to the flow. I have multiple Weksler 5" gauges throughout my RODI system, and an open float against 40 PSI, only drops the pressure by about 10PSI until the 10" or 20" Prefilters/RO/DI drop pressure. IMHO this burst of pressure will blow the conductivity probe.
    Quote Originally Posted by zombie View Post
    Not if you put the solenoid before the probe. Then pressure is less than 1 psi.

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  2. #27
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    Quote Originally Posted by 1jwampler View Post
    I may not understand what you're doing with the solenoid, but, typically they stop or allow flow(not reduce pressure/ this is what a pressure regulator is used for - google Watts P-60), pressure is the resistance to flow, so while closed you are correct there will not be pressure or flow toward the schedule 80 TEE you plan to put the probe in, however, when you command the solenoid to open, the water will flow through the solenoid and apply whatever pressure is available behind the solenoid to keep the flow. So.... assuming your solenoid closes before your float it will receive less pressure, IMHO not 1 PSI even with a float open, as 1/4" tube will provide substantial resistance (Pressure) to the flow. I have multiple Weksler 5" gauges throughout my RODI system, and an open float against 40 PSI, only drops the pressure by about 10PSI until the 10" or 20" Prefilters/RO/DI drop pressure. IMHO this burst of pressure will blow the conductivity probe.
    If someone is investing the money to add a PM2 and cond probe for remote TDS sensing, they are almost guaranteed to invest another $60 to install some floats and a solenoid for auto filling their reservoir. If the solenoid is placed anywhere prior to the cond probe along the piping, then the pressure spike you are referring to happens at the solenoid itself and at that same instant the pressure on the cond probe would be zero because all pressure is blocked by the solenoid. If the solenoid is closed allowing water to flow, only the minor pressure left after the RO membrane drops it can be applied to the cond probe. This remaining pressure is tiny and well under 1 psi, likely even less than 0.1 psi.

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  3. #28
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    Solenoids don’t reduce pressure they stop flow this is basic hydraulics IMHO you’re providing a high risk solution. It would be risk free to mount a probe in a RODI storage tank, which someone making that investment would have.


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  4. #29
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    Quote Originally Posted by 1jwampler View Post
    Solenoids don’t reduce pressure they stop flow this is basic hydraulics IMHO you’re providing a high risk solution. It would be risk free to mount a probe in a RODI storage tank, which someone making that investment would have.


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    Stopping flow and reducing pressure to zero are the same thing. An open solenoid has full pressure on the incoming side and zero pressure on the outgoing. Not a high risk solution if piped correctly.

    Depending on the application, the Tee approach is necessary. For example someone wants to check TDS pre and post DI or if they want to flush with another solenoid until TDS drops below a certain level etc. If all they want is a email notification when their DI resin is exhausted and TDS creeps in the reservoir, I agree putting in the reservoir itself is a better solution.

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  5. #30
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    Quote Originally Posted by zombie View Post
    Stopping flow and reducing pressure to zero are the same thing. An open solenoid has full pressure on the incoming side and zero pressure on the outgoing. Not a high risk solution if piped correctly.

    Depending on the application, the Tee approach is necessary. For example someone wants to check TDS pre and post DI or if they want to flush with another solenoid until TDS drops below a certain level etc. If all they want is a email notification when their DI resin is exhausted and TDS creeps in the reservoir, I agree putting in the reservoir itself is a better solution.

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    A closed solenoid has full pressure on the inbound(ingress) side and no pressure on the outbound(egress) side, an open solenoid at the exact moment of opening has no pressure or flow on the egress side, once open, depending on the egress restriction to flow, will equalize pressure with the ingress side. The only way to have no pressure (< 1 PSI as you say) in this instance is if the egress side of the TEE were in an open container that would take a substantial amount of time to equalize prior to the solenoid closing again, in which case the water level in the TEE would not rise enough to cover the conductivity probe and settle for a proper reading. The Neptune Systems conductivity probe takes several minutes to stabilize and get an accurate reading, something that would not be conducive to this effort.

    Your idea could work if the OP put a TEE before the probe TEE and used a Watts P60 (or the lies) to bring pressure down to 5 PSI or less and use the other other side of the pre-TEE as a bypass, depending on how rapidly he wants to fill. If he can handle filling at 5PSI (which is what you are suggesting would be the case anyhow), then just put a P60 prior to the TEE taking out all of the risk, set the P60 to 5 or less PSI and then no solenoid needed and 100% guarantee not to burst the probe.

    - - - Updated - - -

    Quote Originally Posted by zombie View Post
    Stopping flow and reducing pressure to zero are the same thing. An open solenoid has full pressure on the incoming side and zero pressure on the outgoing. Not a high risk solution if piped correctly.

    Depending on the application, the Tee approach is necessary. For example someone wants to check TDS pre and post DI or if they want to flush with another solenoid until TDS drops below a certain level etc. If all they want is a email notification when their DI resin is exhausted and TDS creeps in the reservoir, I agree putting in the reservoir itself is a better solution.

    Sent from my SM-G965U using Tapatalk
    A closed solenoid has full pressure on the inbound(ingress) side and no pressure on the outbound(egress) side, an open solenoid at the exact moment of opening has no pressure or flow on the egress side, once open, depending on the egress restriction to flow, will equalize pressure with the ingress side. The only way to have no pressure (< 1 PSI as you say) in this instance is if the egress side of the TEE were in an open container that would take a substantial amount of time to equalize prior to the solenoid closing again, in which case the water level in the TEE would not rise enough to cover the conductivity probe and settle for a proper reading. The Neptune Systems conductivity probe takes several minutes to stabilize and get an accurate reading, something that would not be conducive to this effort.

    Your idea could work if the OP put a TEE before the probe TEE and used a Watts P60 (or the likes) to bring pressure down to 5 PSI or less and use the other other side of the pre-TEE as a bypass, depending on how rapidly he wants to fill. If he can handle filling at 5PSI (which is what you are suggesting would be the case anyhow), then just put a P60 prior to the TEE taking out all of the risk, set the P60 to 5 or less PSI and then no solenoid needed and 100% guarantee not to burst the probe.

  6. #31
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    Quote Originally Posted by 1jwampler View Post
    A closed solenoid has full pressure on the inbound(ingress) side and no pressure on the outbound(egress) side, an open solenoid at the exact moment of opening has no pressure or flow on the egress side, once open, depending on the egress restriction to flow, will equalize pressure with the ingress side. The only way to have no pressure (< 1 PSI as you say) in this instance is if the egress side of the TEE were in an open container that would take a substantial amount of time to equalize prior to the solenoid closing again, in which case the water level in the TEE would not rise enough to cover the conductivity probe and settle for a proper reading. The Neptune Systems conductivity probe takes several minutes to stabilize and get an accurate reading, something that would not be conducive to this effort.

    Your idea could work if the OP put a TEE before the probe TEE and used a Watts P60 (or the lies) to bring pressure down to 5 PSI or less and use the other other side of the pre-TEE as a bypass, depending on how rapidly he wants to fill. If he can handle filling at 5PSI (which is what you are suggesting would be the case anyhow), then just put a P60 prior to the TEE taking out all of the risk, set the P60 to 5 or less PSI and then no solenoid needed and 100% guarantee not to burst the probe.

    - - - Updated - - -


    A closed solenoid has full pressure on the inbound(ingress) side and no pressure on the outbound(egress) side, an open solenoid at the exact moment of opening has no pressure or flow on the egress side, once open, depending on the egress restriction to flow, will equalize pressure with the ingress side. The only way to have no pressure (< 1 PSI as you say) in this instance is if the egress side of the TEE were in an open container that would take a substantial amount of time to equalize prior to the solenoid closing again, in which case the water level in the TEE would not rise enough to cover the conductivity probe and settle for a proper reading. The Neptune Systems conductivity probe takes several minutes to stabilize and get an accurate reading, something that would not be conducive to this effort.

    Your idea could work if the OP put a TEE before the probe TEE and used a Watts P60 (or the likes) to bring pressure down to 5 PSI or less and use the other other side of the pre-TEE as a bypass, depending on how rapidly he wants to fill. If he can handle filling at 5PSI (which is what you are suggesting would be the case anyhow), then just put a P60 prior to the TEE taking out all of the risk, set the P60 to 5 or less PSI and then no solenoid needed and 100% guarantee not to burst the probe.
    An RODI into a reservoir is an open system on the tubing output. Since we are talking drip speeds of 6 gph max, there is very little pressure on the egress side of the solenoid while closed. The water level issue could be easily solved by having the probe inverted (cable on underside of tee) and mounted lower in output than the output. A pressure regulator could be beneficial to protect against the rare event that the solenoid fails, a mechanical float stops flow as a backup, and the probe holder tee is not properly pressure rated.

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