Replacement RO Booster Pump

[LLigetfa]

The booster pump on my RO system started to leak. It was also getting very noisy so replace versus repair seems the obvious choice. The dealer that sold me the RO years ago had a slightly different pump to the original.

The original pump was 24V DC and had what looks like two pressure switches in series. I think both are pressure switches but unsure of the functionality. My guess is one of them prevents the pump from starting if the inlet pressure is too high. Can anyone confirm?

The new pump is 24V AC and has only one pressure switch. It came prewired so I did not want to cut and splice in the second existing switch. The pump came with a power supply so I swapped it out. It seems to work fine, turning on when I draw water and turning off when the water is replenished. I've not measured the pressure but it does appear to have more than the old one. I've not checked or adjusted the air precharge on the tank in years.

 

[ditttohead]

Be aware, most pumps are made overseas by the lowest bidder. We only manufacture pumps made by Aquatec for RO boosting. These pumps are a bit more expensive but definitely worth it. Their manufacturing facility is top notch and they take QC very seriously.

As to AC vs DC, this is one of the items that we see coming from overseas, whichever is cheaper... they will use.

I don't really see the need for a booster pump often. What are your water conditions that made you decide to use a booster pump? Typically either very low pressure (less than 40) or very high TDS (over 2000).

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[LLigetfa]

When I bought the RO, I was running 30/50 on the well pump. We run iron filtered and softened water through the RO so not sure on the TDS makeup. I'd guess mostly sodium but don't know the count.

We use a lot of RO water for cleaning and so was concerned about production/recovery times. The cost difference with or w/o the pump was not that much so opted to go with the pump. We would sometimes run out of RO water but wondered if the old noisy pump may have been to blame. I was considering a larger (perhaps a WoW) tank. I'm seeing faster flow out of the dispenser with the new pump and so expect recovery to be faster as well.

The old pump was made in China as is the new one. The manuals that came with them are a poor Engrish translation.

 

[Matt Peiris]

A typical ro system with a booster pump has two pressure switches. A low pressure switch at the inlet (activated or conducting current around 5 psi) makes sure the pump will not run dry. A high pressure switch (deactivated at 40, 60 or 80 psi) cuts off power to the pump when a pressure tank has reached the capacity. You should also have a solenoid valve to stop water supply to the membrane when the pump is off, preventing water running down the drain continuously. Wiring and plumbing diagrams below.

Your new pump probably can run dry like Aquatec 6800 which also operates on 24 VAC. You can upgrade to a larger tank if it fits. There are 4, 5.5, 9, 14 and even 20 gal pressure tanks available.

 

[ditttohead]

We assemble lots of RO systems for pumps for many companies and actually, hate to disagree but most of the companies do not use a low pressure switch, and most do not use a solenoid. Since so many companies are cost based we use a simple high pressure switch only and a traditional ASV instead of the solenoid. The drawing is the preferred way but certainly not the most common way.

A good quality booster pump is not a cheap item, and considering the leak potential of cheap pumps we never recommend them.

I used to work for a company that imported the cheap pumps from China and we tried over a dozen manufacturers, all were basically junk and their primary selling point was that they were the lowest cost. We would test them under industry standard stress testing, some were so bad that they would be removed from the testing protocols before even being wet tested. but, a pump for $9... wow.

When you say WoW, that is a an integrated system design. We have been testing it, so far, so good but I still have a lot more testing to do. it has had many problems during its development over the years but they may have finally gotten all the bugs worked out, time will tell.

 

[LLigetfa]

...most of the companies do not use a low pressure switch, and most do not use a solenoid.

Makes sense that it would be a low cutoff. I would need to put a continuity tester on it with and without pressure to see if it is a low cutoff but given where it is buried in the back, that is not likely to happen. I see no evidence of any solenoid valve.

I wondered what keeps the RO from continually drawing water. There is a gizmo with 4 lines attached and think it might me some kind of metering device that stops the water use when there is no flow of filtered water.

 

[ditttohead]

The "Gizmo" with 4 lines attached is a differential pressure controlled automatic shut off device. When the tank pressure gets up to 60% of the incoming pressure the valve internally closes off the inlet. This will build up pressure on the high pressure switch thereby shutting off the pump. I am not the biggest fan of this design but it works well. I have a drawing somewhere, maybe I will post it later.

 

[Reddart]

View attachment 47244 The "Gizmo" with 4 lines attached is a differential pressure controlled automatic shut off device. When the tank pressure gets up to 60% of the incoming pressure the valve internally closes off the inlet. This will build up pressure on the high pressure switch thereby shutting off the pump. I am not the biggest fan of this design but it works well. I have a drawing somewhere, maybe I will post it later.

With this type of circuit, what I don’t get is how if the pressure sensor is on the tank/permeate side, how does it function if the ASO valve shuts off the pressure first? If the ASO shuts off the feed, how would the pressure switch see the pressure from the pump? Or is there a high pressure switch internal to the pump?

 

[ditttohead]

I am not a fan f this design but it is considered the industry standard. I usually use a solenoid valve instead of the ASOV.

That being said, the pump is supposed to be set at 80 PSI boost pressure. Since the ASOV is a 40-60% On/Off design, when the pressure reaches approximately 48 PSI, the ASV will shut off, the pressure switch is set to shut off at 40 PSI, an 8 pound differential. Basically, the Pump shuts off before the ASV shuts off the inlet. When the 40 PSI switch shuts down the pump, the inlet pressure drops and the ASSV tank side has enough pressure to close off the inlet... A little confusing but it works. I have many customers that prefer this design since it saves a few dollars over the solenoid valve design. On anything over 150 GPD, we always use the solenoid instead.