Need help understanding pressure for RO/DI unit...

[i_declare_bankruptcy]

I have a BRS 100GPD value system that isn't performing well. I'm sure it's my fault.

I have a washing machine line that supplies 80PSI of pressure @ 3/4". I used a 3/4" Y adapter (so now 40PSI out of the end going to RODI) then reduced that down to the 1/4" RODI line diameter. My thinking was that the pressure would then increase significantly after reducing the diameter but now I'm second guessing myself and thinking it's the opposite effect. I'm pretty terrible at understanding fluid dynamics. The performance of the unit is poor and I'm seeing TDS 1.

Is there any way I can supply enough pressure to the unit without a pricey booster pump? Or am I not understanding this?

 

[PDR]

I can't help too much, but I highly recommend getting an inline psi gauge for the RO/DI unit. That way you will know your exact pressure. As long as it's at or over 50 psi you should be fine.

https://www.bulkreefsupply.com/glycerin-filled-pressure-gauge-1-100-psi.html

 

[Super Fly]

sorry but your options are either buy a higher capacity RODI or booster pump... I ended up buying a booster pump and it's made a huge difference in how much faster my RODI now produces water.

 

[i_declare_bankruptcy]

I can't help too much, but I highly recommend getting an inline psi gauge for the RO/DI unit. That way you will know your exact pressure. As long as it's at or over 50 psi you should be fine.

https://www.bulkreefsupply.com/glycerin-filled-pressure-gauge-1-100-psi.html

@PDR you've replied to like every thread I've ever created. Seriously thank you for always offering help and advice... can you get like a 'super excellence award'?

 

[CC13]

I have a BRS 100GPD value system that isn't performing well. I'm sure it's my fault.

I have a washing machine line that supplies 80PSI of pressure @ 3/4". I used a 3/4" Y adapter (so now 40PSI out of the end going to RODI) then reduced that down to the 1/4" RODI line diameter. My thinking was that the pressure would then increase significantly after reducing the diameter but now I'm second guessing myself and thinking it's the opposite effect. I'm pretty terrible at understanding fluid dynamics. The performance of the unit is poor and I'm seeing TDS 1.

Is there any way I can supply enough pressure to the unit without a pricey booster pump? Or am I not understanding this?

1) Water will always flow from the area of high pressure to the area or lower pressure. One is turned 'on' (either the washing machine or the RO/DI), then there would be 80psi of pressure going to that unit. If neither are turned on, there is 80psi in the line. If both are turned on, whichever line has the least restrictions (I would be willing to bet your washing machine inlet lines are far larger than your RO/DI lines), then the majority of the pressure will be going to the area of least resistance between the two units. Again, a washing machine inlet is just water free flowing and dumping into your unit so there would be far less restrictions than in your RO/DI unit where the water is being forced and rammed threw all the filters and membranes. Therefore, your pressure inside the RO/DI would most likely be nowhere close to 80psi.

2) Everytime you use a reducer, your creating a bottleneck. Exactly the same as cars merging onto the highway during rush hour. The merging cars are forcing all the faster highway cars to slow down. Same goes for piping when water is going from a larger diameter pipe into a smaller one. The water is ramming into each other and again you might not be getting the pressure you need.

There is an easy resolution to this. Get a two pressure gauges and install one before the sediment filters and before the RO membrane. You can see what pressures your working with and what happens to the pressure when both the RO/DI and the washing machine are running and again what pressures your working with when just your RO/DI unit is on.

If you pressure to your unit is always 40psi, then your going to need a booster pump.

 

[i_declare_bankruptcy]

1) Water will always flow from the area of high pressure to the area or lower pressure. One is turned 'on' (either the washing machine or the RO/DI), then there would be 80psi of pressure going to that unit. If neither are turned on, there is 80psi in the line. If both are turned on, whichever line has the least restrictions (I would be willing to bet your washing machine inlet lines are far larger than your RO/DI lines), then the majority of the pressure will be going to the area of least resistance between the two units. Again, a washing machine inlet is just water free flowing and dumping into your unit so there would be far less restrictions than in your RO/DI unit where the water is being forced and rammed threw all the filters and membranes. Therefore, your pressure inside the RO/DI would most likely be nowhere close to 80psi.

2) Everytime you use a reducer, your creating a bottleneck. Exactly the same as cars merging onto the highway during rush hour. The merging cars are forcing all the faster highway cars to slow down. Same goes for piping when water is going from a larger diameter pipe into a smaller one. The water is ramming into each other and again you might not be getting the pressure you need.

There is an easy resolution to this. Get a two pressure gauges and install one before the sediment filters and before the RO membrane. You can see what pressures your working with and what happens to the pressure when both the RO/DI and the washing machine are running and again what pressures your working with when just your RO/DI unit is on.

If you pressure to your unit is always 40psi, then your going to need a booster pump.

You're totally right. The static? pressure shouldn't change. I need to remeasure. I got 80PSI out of the line, then with the Y hooked up to a pressure gauge and the washing machine (not running) I got 40... that kinda violates physics haha. Of course I was never planning on making RO/DI water while running the washing machine due to the anticipated pressure drop.

Sounds like I need a booster pump. How do so many people not have booster pumps? they just have crazy high water pressure? I thought 80PSI was good.

 

[Potatohead]

If you have 80 psi at the source I am failing to understand how you only have 40 psi at the unit...?

 

[i_declare_bankruptcy]

Yeah, not enough sleep means bad reasoning. I probably took a bad measurement or the gauge is faulty and have 40PSI at the source.

 

[Potatohead]

truthfully if you need a $120 booster pump it will pay for itself over time because you will use less DI resin and will have less waste water also.

 

[i_declare_bankruptcy]

Set up a gauge today. Getting 45PSI. Booster pump it is

 

[i_declare_bankruptcy]

Oh. Came back and checked and the meter said 95PSI...

So I think this means my regulator is failing and slowly "leaking" pressure into my house's water supply.

I suppose I can replace the regulator and have it set at a higher pressure and then not need the booster pump lol. I mean if the pipes are fine at 95PSI from the failing regulator then they can handle increasing the pressure to ~60-80 PSI from a new regulator?

First house, don't know this stuff so I could be off base. Time for more research.

 

[i_declare_bankruptcy]

Aaaand just to update this incase some poor soul comes across this googling for pressure issues:

Also considering the possibility there's an issue with the expansion tank (or lack thereof -- it's an old house) and that's causing the increase in pressure. If that's the case then a booster pump is necessary. Time to get under the house...

 

[doughboy]

If the rodi output is turned off say via a float valve, and your waste water line does not drip, then you have sufficient input water pressure. If it drips continuously, then you don’t have enough input water pressure.