Ball valve or gate valve for RO system?

[APW]

I put a brand new gate valve on my RO system and adjusted it to try to get the pressure at 180. It always changes higher after a few days. If I put a ball valve on there with that have any effect?

 

[mjwalsh]

Based on experience with balancing pipe flows on a modular boiler system I would say that a ball valve would tend to be the better more durable choice. Not sure on actual pressure changing reliability factor. It seems like on ours there is kind of a valve that makes the pressure less on the gauge after it goes through the membrane ... making much more water flushing to the drain & less going into the make-up water tank.

We have used ports on Gerand ball valves with a metering device & the gpm tends to be consistent but on an open system like city water coming in that could change the dynamic. My guess is that you are checking the pressure when your city water pressure creeps up & it might not be the valve style.

 

[MEP001]

I prefer to use a regulator along with a fixed valve, whether I use it to return a portion of the reject to the pump or to send the reject down the drain. I'd use a ball valve as they generally have a stainless ball and Teflon seals, where a gate valve is brass-to-brass and will erode.

 

[PaulLovesJamie]

I prefer to use a regulator along with a fixed valve, whether I use it to return a portion of the reject to the pump or to send the reject down the drain. I'd use a ball valve as they generally have a stainless ball and Teflon seals, where a gate valve is brass-to-brass and will erode.

My but that was polite

Ball & gate valves are intended to regulate volume of flow (usually to the extreme, ie open/closed.) They will allow fluctuations in the outlet pressure as the inlet pressure changes.
Regulators are intended to regulate pressure.
If you want a consistent 180 psi, use a regulator.
If for some reason you can't use a regulator, a gate valve is easier to make small adjustments, a ball valve is more durable and reliable.

 

[MEP001]

Ball & gate valves are intended to regulate volume of flow (usually to the extreme, ie open/closed.) They will allow fluctuations in the outlet pressure as the inlet pressure changes.

You're right, and if an RO system would perpetually keep the same flow/pressure over time then a simple valve would be fine. And depending on the pump, the system pressure may or may not change depending on the inlet pressure, for example a Procon on the product side doesn't care about inlet side, it will always pump the same GPM as long as it has a sufficient supply. I still prefer a regulator because as the membrane slowly fouls over time and loses product flow, the system pressure will increase if it's set by a ball or gate valve.

 

[washnshine]

FWIW I only have ball valves on everything. Wash and in my home. The gates always leak at the packing nut at some point in time and they have always caused me frustration. My shut offs to my sinks, toilets even garden hose are all ball valves.