RO system slow production after moving house

[TimB]

Hi all. I've just moved to a new home and after setting up my RO system it's running noticeably slower than my last house. The PSI is the same (100) into the 4020 membrane, just slower out the other end than before. I was producing pure at a rate of 1 litre every 36 seconds and now it's 46 seconds. I produce what I need to fill the van each day. The system is on a board I just place into the back of the van. Connected to a 12l Di vessel. I don't have the space, time or money to set up storage for a while.

Anyone have suggestions as to why?

For context: my last house I was able to park adjacent to the pump and tap so everything was very close to the van. Now the tap is farther away by several metres, and that is before it gets to the pump. PSI is then the same, but could that distance be a reason? Everything else is as before. Many thanks for any ideas.

 

[Iron Giant]

You've already given the answer, the longer run of hose is the issue.

 

[TimB]

You've already given the answer, the longer run of hose is the issue.

OK, thanks. I assumed that as the pump then put the pressure into the membrane at 100psi, it didn't really matter what came before that.

 

[TimB]

So that wasn't it. I've shortened hoses and it's still slow so I'm stumped. Coning out of the membrane with a tds of 6 so I barely need my resin. Just slow speed. No idea why.

Maybe the membrane really didn't like being moved.

 

[Pjj]

So that wasn't it. I've shortened hoses and it's still slow so I'm stumped. Coning out of the membrane with a tds of 6 so I barely need my resin. Just slow speed. No idea why.

Maybe the membrane really didn't like being moved.

Have you given it a good flush and no air locks ?

 

[TimB]

Have you given it a good flush and no air locks ?

Each time it starts (this is my third time) it is very intermittent for about 5-10 minutes. Like it's clearing its throat. Then it settles at the slower than normal speed. So you might be onto something with air locks. I always pre flush for a minimum of 50 litres each run.

I wonder if I just let it settle for a week or so if it will improve. I messed with the hoses a couple of years ago and the speed dropped irreversibly. The membrane just seems sensitive to it.

 

[ks789]

It is bizarre, hard to work out some of these things. Logically, you'd say it would have to be pressure drop or maybe flow rate out of the mains, but I think you've covered that? or air lock as suggested?

 

[Pjj]

Each time it starts (this is my third time) it is very intermittent for about 5-10 minutes. Like it's clearing its throat. Then it settles at the slower than normal speed. So you might be onto something with air locks. I always pre flush for a minimum of 50 litres each run.

I wonder if I just let it settle for a week or so if it will improve. I messed with the hoses a couple of years ago and the speed dropped irreversibly. The membrane just seems sensitive to it.

I would put it on maximum flush for a while see if it’s spitting air then grade close the waist down and try that , I had a similar issue when I changed my system from one van to another once the air lock was gone and it was fine but was awkward to get rid of it it’s been fine ever since

 

[TimB]

I would put it on maximum flush for a while see if it’s spitting air then grade close the waist down and try that , I had a similar issue when I changed my system from one van to another once the air lock was gone and it was fine but was awkward to get rid of it it’s been fine ever since

That's a good plan. I'll do that tomorrow or Thursday, give it a long flush, maybe for 15 mins or something. RIP my water bill

 

[TimB]

It is bizarre, hard to work out some of these things. Logically, you'd say it would have to be pressure drop or maybe flow rate out of the mains, but I think you've covered that? or air lock as suggested?

Flow rate is fantastic out of the mains. I used to get 12 litres per min and now its 18. The pressure here is much better. I'm putting about 2.7 litres down the drains for every 1 in pure. Used to be 2.2 I think.

 

[spruce]

Flow rate is fantastic out of the mains. I used to get 12 litres per min and now its 18. The pressure here is much better. I'm putting about 2.7 litres down the drains for every 1 in pure. Used to be 2.2 I think.

When my 4040 was brand new, I got just short of 2 litres a minute of pure. A 4021 is half the capacity, so I would have suggested producing a litre of pure every 48 seconds is good.
I would try to reduce my waste a tad if this was me, and see if this makes any difference.

 

[TimB]

When my 4040 was brand new, I got just short of 2 litres a minute of pure. A 4021 is half the capacity, so I would have suggested producing a litre of pure every 48 seconds is good.
I would try to reduce my waste a tad if this was me, and see if this makes any difference.

Sorry if this is a dumb question, but how do you reduce the waste without increasing the pressure exponentially? I've had people say that before, but closing the waste valve causes the psi to skyrocket for not much gain. 100 psi is optimum for a 4021 membrane I was told.

 

[spruce]

Sorry if this is a dumb question, but how do you reduce the waste without increasing the pressure exponentially? I've had people say that before, but closing the waste valve causes the psi to skyrocket for not much gain. 100 psi is optimum for a 4021 membrane I was told.

Yes, closing the waste valve a tad will change the water to our ratio.

On some booster pumps there is a way of adjusting the output pressure.
Purefreedom added a mechanical bypass valve to their systems. It bled the pressure from the outlet back to the inlet which you adjusted with a ball valve.
Is there a pressure relief valve in the head of the pump that can be adjusted?

 

[Iron Giant]

Sorry if this is a dumb question, but how do you reduce the waste without increasing the pressure exponentially? I've had people say that before, but closing the waste valve causes the psi to skyrocket for not much gain. 100 psi is optimum for a 4021 membrane I was told.

You aren't going to increase the pressure that much, you'll only be closing the waste valve in small increments a 1/2 inch turn or less at a time, it's no different to setting the correct ratio after flushing