Low pressure ..effects on Ro

[Gasket]

Guys,

Couple of times a week I’ve been filling up round the corner at my brothers who’s not on a metre. His water pressure is very low around 30 psi. Obviously it’s taken an age to fill the van, but that doesn’t bother me Cos it’s say there for well over 12 hours anyway. But my question is , is this low pressure causing premature damage to my system at all ??

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[Part Timer]

I doubt it very much, it won't however operate very efficiently and would think it would struggle to get the TDS down to a reasonable number. You will therefore be using a fair bit more resin 

 

[RWCleaning]

No it wouldn’t do any damage, if you wanted to get a booster pump, mine was £300 including a transformer (which you need) it get my pressure up from 20/22psi to 65/70. But you can’t run it continuously, I have a timer switch, 1hr on 1hr off. 

 

[Guest]

Low pressure will shorten the life of the RO membrane


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[Part Timer]

Low pressure will shorten the life of the RO membrane


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 Not being awkward but why? Just inquisitive

 

[P4dstar]

 Not being awkward but why? Just inquisitive

I have seen this somewhere else before. As i'm running on quite low pressure at the mo I would be interested to know also. Perhaps @spruce or @doug atkinson could give us some insight?

 

[Stevieboy]

No it wouldn’t do any damage, if you wanted to get a booster pump, mine was £300 including a transformer (which you need) it get my pressure up from 20/22psi to 65/70. But you can’t run it continuously, I have a timer switch, 1hr on 1hr off. 

£300 for a booster pump. Why don’t you just use a 100 psi 12v pump running from a battery in your van? No mains required. Fill up anywhere on the fly, all you need is an outside tap. 

 

[spruce]

I have seen this somewhere else before. As i'm running on quite low pressure at the mo I would be interested to know also. Perhaps @spruce or @doug atkinson could give us some insight?

Does low pressure damage a membrane? I honestly don't know the answer to that one. Sorry.

The r/o will not be running as efficiently as it would at a higher pressure so I would tend to believe that the membrane might clog up a bit quicker with calcium deposits and hence reduce the service life of the membrane. Would a low water pressure not be as effective when flushing? I believe so.

Damage to membrane material is a chlorine related issue.

At a low water pressure you would again need to adjust your pure to waste ratio. You might even have to go lean on the waste which will again reduce the service life of the membrane and add to your resin costs.

 

[Dave B]

I killed a set of membranes on my 450gpd in only around a year and they were completely caked up with deposits 

It coincides perfectly with when my water pressure was lowered from 73 to 35 psi

I don't think they ever flushed effectively at that pressure as I always flush a couple minutes each day before use and a proper flush at weekend

Got a booster pump now and have no issues

 

[spruce]

£300 for a booster pump. Why don’t you just use a 100 psi 12v pump running from a battery in your van? No mains required. Fill up anywhere on the fly, all you need is an outside tap. 

I've seen that done with a small 300GPD r/o. I've put a photo up of a setup I saw on here over a years ago.

But it would get much more complex with a bigger 4040 r/o.

Running a 5.2lpm Shurflo pump would be a balancing act to get the right flow at the right pressure. So I would see a need to add an analogue controller into the mix. At 60psi the specs tell us that a Shurflo pump will draw 7.2amps, so using a Shurflo pump continiously from a 12v battery would draw a fair bit of current and add additional strain on a standard 75amph leisure battery. At 60psi that pump will just manage to deliver 4.7lpm of water which might just be a little shy of the requirements the r/o needs.

The other point to consider is that the maximum inlet pressure on a Shurflo pump is 30psi.

Have you done this yourself @Stevieboy and how has it worked for you?

 

[P4dstar]

£300 for a booster pump. Why don’t you just use a 100 psi 12v pump running from a battery in your van? No mains required. Fill up anywhere on the fly, all you need is an outside tap. 

You can’t use that sort of thing on a 4040 RO mate.


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[Stevieboy]

You can’t use that sort of thing on a 4040 RO mate.


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Yep got this in my van on a 40/40. 3.5 litres min pure output. 

 

[spruce]

Yep got this in my van on a 40/40. 3.5 litres min pure output. 

Please tell us what pump you are using and how you have set it up. Thanks

 

[Stevieboy]

Yep got this in my van on a 40/40. 3.5 litres min pure output. 

Why ever not. Pressure is pressure mate. 

 

[Stevieboy]

You can’t use that sort of thing on a 4040 RO mate.


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Why ever not mate. Same as what you are doing? Booster pump?

 

[P4dstar]

Running a 5.2lpm Shurflo pump would be a balancing act to get the right flow at the right pressure. So I would see a need to add an analogue controller into the mix. At 60psi the specs tell us that a Shurflo pump will draw 7.2amps, so using a Shurflo pump continiously from a 12v battery would draw a fair bit of current and add additional strain on a standard 75amph leisure battery. At 60psi that pump will just manage to deliver 4.7lpm of water which might just be a little shy of the requirements the r/o needs.

@Stevieboy Spruce has given the science behind it. We're all open to finding a way to make it work mate. My thoughts come from recommendations from all the major suppliers and the fact that even on it's max setting my 100PSI Shurflo won't supply my pressure washer the same way my tap with sub 50PSI does.

 

[spruce]

@Stevieboy Spruce has given the science behind it. We're all open to finding a way to make it work mate. My thoughts come from recommendations from all the major suppliers and the fact that even on it's max setting my 100PSI Shurflo won't supply my pressure washer the same way my tap with sub 50PSI does.

Brodex has a portable battery operated 4040 with a Shurflo pump driving the system. Question is; which Shurflo pump are they using?

https://brodexbms.co.uk/product/portapower-trolley-system-12v/

So it is possible, hence the reason for asking a bit more detail from @Stevieboy.

The points of interest to me are;

It produces 200lph of pure water and they set the waste to pure ratio at 30 to 40% waste.

At 50 psi my 4040 delivers 2lpm (120lph) with 2 liters of waste, a 50/50 pure to waste ratio.

So what Brodex are doing is restricting the waste to get more pure at the expense of pure quality, but supply a large di vessel to mop up all those extra ppm the waste water doesn't flush away. But don't anyone worry, if Brodex are up to their old tricks, chlorine will destroy the membrane before it clogs up as they don't supply a carbon block filter prefilter, only a sediment filter. And, if they remove the O Ring from the head of the di vessel that seals the downpipe to the lower filter basket then the resin will stop working sooner and they will get a new resin order sooner.

So to me using a 12v Shurflo pump driven by the on board leisure battery is possible but not a long term solution. But I maybe wrong, so hence the request for more info on @Stevieboy's system setup.

 

[P4dstar]

Brodex has a portable battery operated 4040 with a Shurflo pump driving the system. Question is; which Shurflo pump are they using?

https://brodexbms.co.uk/product/portapower-trolley-system-12v/

So it is possible, hence the reason for asking a bit more detail from @Stevieboy.

The points of interest to me are;

It produces 200lph of pure water and they set the waste to pure ratio at 30 to 40% waste.

At 50 psi my 4040 delivers 2lpm (120lph) with 2 liters of waste, a 50/50 pure to waste ratio.

So what Brodex are doing is restricting the waste to get more pure at the expense of pure quality, but supply a large di vessel to mop up all those extra ppm the waste water doesn't flush away. But don't anyone worry, if Brodex are up to their old tricks, chlorine will destroy the membrane before it clogs up as they don't supply a carbon block filter prefilter, only a sediment filter. And, if they remove the O Ring from the head of the di vessel that seals the downpipe to the lower filter basket then the resin will stop working sooner and they will get a new resin order sooner.

Not that you're sceptical eh Spuce ?

I've just followed that link. They've just smashed £400 of kit onto a £30 sack truck and they're selling it for nearly 3 grand. We're in the wrong business @spruce

 

[ks789]

Does low pressure damage a membrane? I honestly don't know the answer to that one. Sorry.

The r/o will not be running as efficiently as it would at a higher pressure so I would tend to believe that the membrane might clog up a bit quicker with calcium deposits and hence reduce the service life of the membrane. Would a low water pressure not be as effective when flushing? I believe so.

Damage to membrane material is a chlorine related issue.

At a low water pressure you would again need to adjust your pure to waste ratio. You might even have to go lean on the waste which will again reduce the service life of the membrane and add to your resin costs.

Yes but ive found when I cut down on the waste which increases the pressure, the tds doesnt go as low, thereby using up more resin. I did have pressure at about 55 on my 4021, but now if I have that the tds is 18 odd before the di. So Ive reduced the pressure at the cost of more waste, down to 45 and the tds is 13 before the di. (this is 530 out the tap mind) So like has been said, more water bill or longer lasting resin? Also, how to know the pressure for the flush? the pressure only goes up when the valve/tap is closed to start the pure coming out.

 

[spruce]

Yes but ive found when I cut down on the waste which increases the pressure, the tds doesnt go as low, thereby using up more resin. I did have pressure at about 55 on my 4021, but now if I have that the tds is 18 odd before the di. So Ive reduced the pressure at the cost of more waste, down to 45 and the tds is 13 before the di. (this is 530 out the tap mind) So like has been said, more water bill or longer lasting resin? Also, how to know the pressure for the flush? the pressure only goes up when the valve/tap is closed to start the pure coming out.

The theory is that the higher the tap water pressure the higher the flow rate from the tap, all being equal. A 4040 on flush has very little pressure in the system. Our gauges drop from 50 psi to just around 5 psi and that's on both sides of the prefilters. If you turn your hose tap off the water pressure builds up until its equal through the length of the hose to the tap. If you open that fully the water pressure of the water leaving the end of the hose is zero. If the hose can transport more water than the system/pump can deliver then the pressure in the hose will drop off accordingly.

 If your tap water pressure is low to start with, the force to drive the water through the r/o is low and hence the flush isn't going to be as good.

 

[ks789]

Hopefully the flush is ok. As it is, on balance think I'll stick with the pressure reduced a bit to get lower reading pre di, and get stung a bit on water waste. Bit like juggling really, or robbing peter to pay paul lol