RO or DI advice please?

[Deleted member 5762]

Hello,

I’ve been using spotless water for my pure water, as I don’t need it all the time.

Rather than taking the trip a few times a week I wanted to ask if I am best to buy either a smallish RO system, or whether to use double DI.

My TDS is around 280, so on paper I’d be better with an RO, however I don’t use that much pure water (anything between about 20 and 50 litres a day, and sometimes not even that), so I don’t want to buy an RO system if it only needs to be turned on once or twice a week for a couple of hours if it would cause any issues with it.

I wasn’t sure the cost would make much difference if I’m not using that much pure water.

Any tips would be much appreciated.

 

[ched999uk]

One other thing you need even with a little RO is water pressure. You really need 50psi or above to get best flow out of an RO.
When I started I bought a 150GPD (US Gallons Per Day) RO for about £100 I think. It produced about 10 litres an hour of pure on my tap pressure of 28psi! I bought a booster pump (£70) and the output increased to about 20 litres an hour. I used a wheelie bin as a pure storage container but after a few weeks it split due to the weight of water! So then I bought a water butt and that worked perfect. You do need to put some water through an RO regularly to stop it drying out!
I think GrippaTank have a resin calculator that might help you decide how much a DI would costs to run per month.
One thing to remember is that a small RO uses about 3 litres of water to produce 1 litre of pure, water isn't that expensive but you also have the additional sewerage charges as that's based on the water through the meter (you can fit an extra meter to show Water company you are taking some off site but I doubt that is worth it for such small amounts.

Sorry if that's not a straight answer but hopefully it gives you something to thing about.

 

[Deleted member 5762]

One other thing you need even with a little RO is water pressure. You really need 50psi or above to get best flow out of an RO.
When I started I bought a 150GPD (US Gallons Per Day) RO for about £100 I think. It produced about 10 litres an hour of pure on my tap pressure of 28psi! I bought a booster pump (£70) and the output increased to about 20 litres an hour. I used a wheelie bin as a pure storage container but after a few weeks it split due to the weight of water! So then I bought a water butt and that worked perfect. You do need to put some water through an RO regularly to stop it drying out!
I think GrippaTank have a resin calculator that might help you decide how much a DI would costs to run per month.
One thing to remember is that a small RO uses about 3 litres of water to produce 1 litre of pure, water isn't that expensive but you also have the additional sewerage charges as that's based on the water through the meter (you can fit an extra meter to show Water company you are taking some off site but I doubt that is worth it for such small amounts.

Sorry if that's not a straight answer but hopefully it gives you something to thing about.

Thank you very much. My water pressure is OK-ish (tested it with a pressure tester) but I’d definitely buy a pumped unit anyway.

That was my worry - if I didn’t need it for a week or more it would sit there and I might cause it to have a problem.

 

[ched999uk]

Thank you very much. My water pressure is OK-ish (tested it with a pressure tester) but I’d definitely buy a pumped unit anyway.

That was my worry - if I didn’t need it for a week or more it would sit there and I might cause it to have a problem.

I am no membrane expert but I would guess a week would be OK. One thing to think about is future use, i.e do you think your water usage would increase?
If you go for a non pumped system it would have to operate more to make your pure so that might be less days for it to dry out, also I guess if you made the pure and waste pipes have a slight upward curve when they come out of the RO it might help it not to drain and maintain some water in.
If I remember correctly I used to use mine for a day to fill water butt then not use it for a few days maybe a week and mine was fine.

 

[Pjj]

With a TDS of that ro is the best way forward otherwise you will be getting through resin at a rate of nots speak to Doug at daqua he is a good honest guy and will Point you in the right direction, it won’t hurt if it’s not used every day , as a rule of thumb if TDS is over 90-100 ro is best and cheapest way in the long run

 

[Deleted member 5762]

With a TDS of that ro is the best way forward otherwise you will be getting through resin at a rate of nots speak to Doug at daqua he is a good honest guy and will Point you in the right direction, it won’t hurt if it’s not used every day , as a rule of thumb if TDS is over 90-100 ro is best and cheapest way in the long run

Thanks @Pjj . I’m ok with either option, it’s more the fact if I knackered the RO if I didn’t need to use it for a while. I also have no soakaway so possible problems with the water board as the waste would have to go down the drain.

 

[scottish cleaning service]

My TDS is 75 ppm and they said I was borderline between RO and Di. I am glad I went for RO because I haven't bought resin since I started wfp 3 years ago. Oliver replaces the resin when I get a yearly service.

 

[Deleted member 5762]

My TDS is 75 ppm and they said I was borderline between RO and Di. I am glad I went for RO because I haven't bought resin since I started wfp 3 years ago. Oliver replaces the resin when I get a yearly service.

Thank you. I’m only basing it on the fact I use a very small amount of pure water compared to most.

 

[Part Timer]

For the quantity you use just use a.DI. the.faff on of setting up, even a 250gpd, R/O isn't required yet.

 

[Deleted member 5762]

For the quantity you use just use a.DI. the.faff on of setting up, even a 250gpd, R/O isn't required yet.

@Part Timer thank you very much