Resin vessel slow water production rate?

[GW2021]

Hello,

I've noticed that putting our ro water (after it's come out of the sequence of three membranes) through a 10 inch resin vessel considerably slows the production rate. I've carried out some timings:

Without using the resin vessel, it takes approximately 90 seconds to produce a litre of water;

If I put it through the 10 inch resin vessel, it takes almost 4 minutes to produce a litre of water. 

This is making a big difference to the time it takes to produce the water we need for our window cleaning. I'm sure it didn't use to make much of a difference to the production rate, whether we used the resin vessel or not. Cleaning Spot offers this comment: 'Resin does not slow down the water flow very much at all, so for normal flow rates the resin will not make any noticable difference to the speed of the water, or the pressure. If you find the water pressure is low after the resin vessel it's probably due to air in the vessel. If this is the case just unscrew the vessel a tiny bit, to allow the air to escape'. I don't think there's a problem with air in the vessel.

Has anyone else noticed that using a resin vessel slows production noticeably? The water is coming out of the three-sequence membranes at around 15 ppm, so I really need to use resin to get the product water to nearer to 0 ppm. Water pressure off of the mains is reasonable. I'm not sure if anything could go wrong with a resin vessel, and whether it's worth trying a replacement.

Thanks if anyone has any suggestions,

GW

 

[Part Timer]

We produce between 3 and 5 litres a minute from a 40/40 boosted R/O using a DI. No noticeable difference of water volume pre or after DI vessel.

 

[ched999uk]

Make sure that the inlet and outlets of the 10" resin vessel are clear of obstructions! It could be that resin is clogging the outlet slowing things down.

When you say 'sequence of three membranes' I assume they are in parallel not in series? What size are the membranes? 90sec for a litre for 3 membranes in parallel even if only 150gpd seems slow. When you say water pressure is OK is it above 80psi? What is your input tds?

 

[Pjj]

 You arnt going to purify much water with a 10 inch di can you not put it through a proper vessel ???

 

[CMcB]

A 10inch di is probably a cartridge. If the resin is tightly packed (which it should be) i would think that it would slow down the flow. If its a relatively small ro the flow won't be high anyway so it'll make a big difference. In a bigger di vessel the resin is loose so it wouldn't impede the flow so much. 

Though I don't know if anything I said is true! But that would be a possibility I think ?

 

[Clearview Lee]

Interesting. I’ve found the production of pure water considerably slower since adding a DI Vessel to proceedings too! 
I used to have it in the van, but moved it into my garage to minimise flow problems while at work. 
 

 

[GW2021]

Thanks for the replies everyone. We have three 10 inch RO membranes in the system. The waste from membrane 1 goes into membrane 2, the waste from membrane 2 into membrane 3, and the product water is combined in one outlet in the system as it goes.

The pressure gauge gives a reading of around 60 psi. Input tds of the water is around 280 ppm, and the combined output of the three membranes is about 15 ppm (the membranes were changed 20 months ago). We have a combined sediment and chlorine pre-filter.

Our system is inside our home (with the product water stored in an outside 1000 litre holding tank), so there's no space for a larger di vessel. It lasts quite a few days between changes though, as the water going in is only around 15 ppm.

The resin is contained within a cartridge inside a 10 inch canister. I'll have a good look to see if there are any blockages in the cartridge or the canister, but I've never noticed anything. One quirk I've noticed is that the sponge in the cartridge (which I think is there to prevent channelling through the resin) always ends up at the bottom of the cartridge, even though I put it at the top, under the screw-top lid. I assume water pressure forces it through.

I'm sure we didn't used to have this slow production problem, and leaving the water producing overnight used to mean the tank would be more than half full by the morning - now it seems to only be about a third full.

Thanks again for your thoughts.

 

[ched999uk]

I'm no expert just read lots, especially on here but if one of your membrane is 95% efficient (95% isn't a particularly high fig for an RO) then the tds out should be 14tds! So I would start by testing the out put of each ro as I suspect maybe one or more are clogged up. How often do you flush them? The 2nd and 3rd will be getting very high TDS so they might be a clogged up. 

I don't think many people put 3 ro in series with each other. I guess you are trying to cut down on waste water? 

I have never quite worked out if running ro's in series is a good idea as I'm not sure how much pressure you actually get on 2nd let alone 3rd.

I would just connect 1 ro up at a time and see if any flow faster or slower than each other.

I think the di sponge is to stop the resin leaving the di vessel, so if its moving that might enable blockages to happen maybe even in the pipework to your tank?

 

[Iron Giant]

You need a decent sized DI Vessel to take it down to 000ppm with correct fittings, to speed up production, or you stick with what you've got or buy a booster pump, personally with a tap tds of 280ppm I think you should have bought a 40/40 R/O

 

[Part Timer]

Thanks for the replies everyone. We have three 10 inch RO membranes in the system. The waste from membrane 1 goes into membrane 2, the waste from membrane 2 into membrane 3, and the product water is combined in one outlet in the system as it goes.

The pressure gauge gives a reading of around 60 psi. Input tds of the water is around 280 ppm, and the combined output of the three membranes is about 15 ppm (the membranes were changed 20 months ago). We have a combined sediment and chlorine pre-filter.

Our system is inside our home (with the product water stored in an outside 1000 litre holding tank), so there's no space for a larger di vessel. It lasts quite a few days between changes though, as the water going in is only around 15 ppm.

The resin is contained within a cartridge inside a 10 inch canister. I'll have a good look to see if there are any blockages in the cartridge or the canister, but I've never noticed anything. One quirk I've noticed is that the sponge in the cartridge (which I think is there to prevent channelling through the resin) always ends up at the bottom of the cartridge, even though I put it at the top, under the screw-top lid. I assume water pressure forces it through.

I'm sure we didn't used to have this slow production problem, and leaving the water producing overnight used to mean the tank would be more than half full by the morning - now it seems to only be about a third full.

Thanks again for your thoughts.

Can you not just remove the resin cartridge and stick an 11 litre DI on top of your storage tank.