Puzzled by tds reading.

[spruce]

The fact the TDS is 286 from a previous reading of 282 means nothing, you could take 10 readings one after another from your tap and they would all be different. Your R/O membrane is still removing 96% of the solids so is still working ok. What size resin bottle do you use, and when was the resin last changed.

Agree 100%. One of the early wfp suppliers advised me that in his opinion the cut off point for membrane replacement was 94%. So @Jango's membranes are closing in on that figure. The higher the rejection rate from the membranes the more resin one will use the polish the water off. But I would personally make the change earlier if my in coming tap water tds was high. My reasoning would be that I'm going to have to replace membranes just now anyway, so do it now and save the extra resin costs. Its all about 'economies of scale.' Is @Jango still better off financially saving money on not replacing membranes and spending a little extra on resin. Effort must also be included as part of the 'economies of scale' decision.

 

[Jango]

So Spruce, you think the membrane is on its way out then. It's only 18 months I was told, when I bought the second hand system. So you think everything needs replacing. What about di to bigger vessel from 6.5 litre? Many thanks

 

[Iron Giant]

 
That would depend on the sediment content of your water. Theoretically, a sediment filter could last for years if there was no sediment in the water. The reason a carbon block filter has a service life is that it can only absorb and finite amount of chlorine. Most change their sediment filter when they change their carbon filter. For us in our area we do have heavy sediment issues in our water from time to time. Something was definitely going on a couple of years ago as I was replacing a sediment filter every month and the carbon block on schedule at every 3 months based on the water we were using then.
 
The only way I tell if the sediment filter is prematurely blocking up from sediment is comparing the water pressure gauges I have on each side of the prefilters. Our WP is 50psi and when the gauge after the prefilters drops to 40psi I change the sediment filter. If the carbon block is just about ready to change then I will do both as reset the water meter. I have clear prefilter bowls and within a few hours of producing water after a prefilter change I can already start to see the sediment filter changing colour.
 
Many years ago one of the local lads phoned me up to ask for help as his RoMan type r/o wasn't producing water any longer even with a booster pump. When I open the sediment filter housing it was chocker with sediment. He told me he had changed his filters several months before. Replacing filters solved the problem.
 
 

Don't have an issue with sediment at all, I just have one as a precaution

County Durham Lad

 

[Iron Giant]

So Spruce, you think the membrane is on its way out then. It's only 18 months I was told, when I bought the second hand system. So you think everything needs replacing. What about di to bigger vessel from 6.5 litre? Many thanks

It might only be 18 months old but it's about how much water it has processed within that time frame the other guy could have had it running 24hrs a day 7 days a week.

County Durham Lad

 

[Jango]

It might only be 18 months old but it's about how much water it has processed within that time frame the other guy could have had it running 24hrs a day 7 days a week.

County Durham Lad
 

He only worked part time, it wasn't producing everyday, only did 3 part days. But I guess it's one of those things. 

I have checked back and my pre-filters went in on the 15th June, so they will need changing.

how long do I need to flush them for, is it around an hour or so? 

 

[ks789]

I reckon the membrane can deteriorate if not in use for too long or left dry, not too sure on this though. If its had all un-pure tap water in it, then been left a while you'd think this could be a cause of trouble. All you can do is try. Yep, flush through all to waste after membrane and see.

 

[spruce]

So Spruce, you think the membrane is on its way out then. It's only 18 months I was told, when I bought the second hand system. So you think everything needs replacing. What about di to bigger vessel from 6.5 litre? Many thanks

I bought a second hand system when I first started wfp and that was a year old. The membranes were also on their way out (which I didn't know) as the original owner never replaced prefilters in the time he owned it. He did it for me but it was too late by then. I learnt a valuable lesson. Never buy a second hand r/o and if you are tempted only pay the second hand value of the housings - be prepared to have to buy new filters and membranes and take that into consideration when determining a price. In most cases the result will be to buy a new one to begin with.

Sellers will say anything to make you happy about the price they are asking. You know the drill; "this is a one owner car lovingly looked after by a careful old lady."

I have a 6.5 liter di vessel and its fine for me. My pure after r/o is 2 to 3ppm so a I only replace resin once a year on average. The bigger the di vessel the longer the time between resin changes, but it also means its heavier and bulkier when trying to empty the resin from the di vessel when you do have to change it.

 

[Jango]

Many thanks to everyone for helping me out.