sharpener Posted June 28 Share Posted June 28 I have a 5000 litre underground rainwater tank which collects almost everything that comes off 200 sq m of slate roof in a village in Devon, which amounts to over 200 cu m per year. It goes through multiple stages of filtration and then a UV steriliser. So it is fit to drink, though in fact we have mains water piped to the cold taps for drinking. Everything else gets fed from the rainwater - loos, washing machine, dishwasher, hot water system. The water is noticeably acid and the stainless steel spring in the UVC pressure regulating valve has in the past completely disintegrated. The acidity is because of the CO2 that gets dissolved from the atmosphere as the rain falls through it. I have used the free Aqion s/w to investigate this (www.aqion.de) and it gives the equilibrium pH as 5.61. Testing the as-collected water with pH strips is not reliable (because of the low conductivity), but I have found the Universal Indicator drops available from Amazon give a clear indication with a resolution of 0.5 pH. Typically it is pH 6.0 or less. I have had conflicting advice about this and currently dose it with 100g of sodium bicarbonate per 1000 litres. Even so it doesn't get much above pH 7.0 (though aquion predicts 8.28). Does anyone else see this as a problem or do anything to treat their harvested water? Link to comment Share on other sites More sharing options...
sam Posted June 28 Share Posted June 28 I treat my acidic spring water with a cylinder containing a product called Juraperle. It needs topping up every 6 months or so. I've not found universal indicator strips particularly useful but when the drinking water starts to taste a bit metallic its a sign I need to top it up. Link to comment Share on other sites More sharing options...
SteamyTea Posted June 28 Share Posted June 28 Interesting. I have the same rain as you, just more of it, because I am in Cornwall. I have often thought that a bit of rainwater harvesting could be useful, but also worried about the quality of the rain. I may try collecting a bit and get a pH test kit and see what it is really like. I have a microscope so can look at the 'dirt' in it quite easily. Link to comment Share on other sites More sharing options...
sharpener Posted June 28 Author Share Posted June 28 2 hours ago, sam said: I treat my acidic spring water with a cylinder containing a product called Juraperle. It needs topping up every 6 months or so. I've not found universal indicator strips particularly useful but when the drinking water starts to taste a bit metallic its a sign I need to top it up. Have been sold loose Juraperle in the past but not found a good way of dosing it. Cylinder sounds interesting, do you have a link? 1 hour ago, SteamyTea said: I may try collecting a bit and get a pH test kit and see what it is really like. I have tried various things and recommend the liquid indicator drops, they give a much more positive pH indication than any strip. Have also used the 10-in-1 test kits from Simplex Health, they are quite sensitive tests for various metals and contaminants inc bacteria. But their pH strips are pretty useless. Link to comment Share on other sites More sharing options...
Conor Posted June 29 Share Posted June 29 I'd switch your UVC to mains supply. I'm assuming the plumbing to washing machines, toilets etc is mostly copper and plastic? Then that level of acidity won't be an issue. I'm assuming you have this setup for reasons other than economic? Is the mains water particularly hard? I'm thinking that a pH treatment system, and it's maintenance etc will cost more than the additional ~100l a day to feed your hot water needs. Link to comment Share on other sites More sharing options...
JohnMo Posted June 29 Share Posted June 29 16 hours ago, sharpener said: water is noticeably acid Don't you need something like this? https://silverlineuk.co.uk/product-category/well-water-treatment-borehole-water-filter-systems/ph-correction-units/ Link to comment Share on other sites More sharing options...
sharpener Posted June 29 Author Share Posted June 29 5 hours ago, Conor said: I'm assuming you have this setup for reasons other than economic? Is the mains water particularly hard? I'm thinking that a pH treatment system, and it's maintenance etc will cost more than the additional ~100l a day to feed your hot water needs. It's historical, the previous owners had installed it, with many deficiencies, sorting it out was quite a project but we anyway needed to get new surface water drains put in after the garage was flooded. In hindsight we should probably have binned it, though (after the cost of consumables) the savings on water and sewerage charges are £100s a year. 5 hours ago, Conor said: I'd switch your UVC to mains supply. I'm assuming the plumbing to washing machines, toilets etc is mostly copper and plastic? Then that level of acidity won't be an issue. UVC is stainless steel so that is not the problem. We do need to treat the water anyway to avoid it dissolving copper from the cold pipework. Then the hot pipework is OK provided we do not exceed 55C. Not bothered about legionella. 6 minutes ago, JohnMo said: Don't you need something like this? https://silverlineuk.co.uk/product-category/well-water-treatment-borehole-water-filter-systems/ph-correction-units/ Perhaps. Have spoken to them in the past. The standard size we would need for a whole-house supply is 4ft 6ins high by ?10 ins diameter which is too big to go in the existing kiosk in the garage with the 2 filters and pump in it. Would also need auto-backwash on a timer, with a drain connection as well. 16 hours ago, sam said: I treat my acidic spring water with a cylinder containing a product called Juraperle. Something more like this perhaps? https://www.ebay.co.uk/itm/374794124532. Only 3 litres/min flow rate though. Contact time with Juraperle is the issue, hence the height of the whole-house system vessel you need. Its advantage is that being calcium carbonate based its action is self-limiting to ?ph 8.5 so does not continue to dissolve indefinitely. Magnesium-based pH correction media like Corrosex are much faster but have an end pH of 10.0 (drinking water limits are 6.5 to 9.0) so not advisable on their own. Mixtures of 90/10 or 75/25 are recommended as a compromise but if you are away the magnesium component continues to dissolve making the water too alkaline. We have not found a foolproof way round all this at a reasonable installed price despite consulting several different equipment suppliers and a water quality testing specialist. And the water treatment firm who supplied all the kit for a local vineyard and winery(!) They proposed a bag filter containing Juraperle placed in the tank inlet pipe, but after a very long wait the one they then supplied was too big to fit. Link to comment Share on other sites More sharing options...
JohnMo Posted June 29 Share Posted June 29 16 minutes ago, sharpener said: garage with the 2 filters and pump in it. Would also need auto-backwash on a timer, with a drain connection as Backwash may not be required if you are already filtering debris (turbidity) upstream. The backwash is only there to get rid of debris if used for filtering also. Link to comment Share on other sites More sharing options...
sharpener Posted June 29 Author Share Posted June 29 18 minutes ago, JohnMo said: Backwash may not be required if you are already filtering debris (turbidity) upstream. You may be right but even so it is a comparatively big and expensive extra vessel, according to the GAPS Water Treatment web site we would need the 13 x 54 inch size for 20 l/min. We have 5 micron and 1 micron filters upstream so the treated rainwater is in fact clearer than the mains water, which often throws deposits. The 1 micron one will soon need changing, we will replace the activated plant charcoal cartridge with one containing bone char which we have been told is better at reducing the iron content, another issue though no-one has any idea where it comes from as there is none in the system, it is all s/s, brass or plastic. Have just noticed this footnote on the GAPS site "*Note: If the inlet water contains iron or manganese it is recomended to use a backwashing unit instead to prevent media binding." Somewhere I also read that the backwash also serves to shake up the bed, wash out spent fines and expose fresh calcite surfaces to the incoming flow. The tank has a 4 in vertical inlet pipe going right to the bottom, the designers say this helps to aerate and stir the contents and prevent it becoming stagnant. So ATM we have been feeding Juraperle down this pipe, the thinking was the inflow would also spread the Juraperle about too. It seems to do that but still does not raise the pH by the expected amount so we continue with the bicarbonate which is pre-dissolved and fed down a small bore plastic pipe into the inlet. Link to comment Share on other sites More sharing options...
Hastings Posted July 1 Share Posted July 1 On 28/06/2024 at 19:14, sharpener said: Testing the as-collected water with pH strips is not reliable (because of the low conductivity), but I have found the Universal Indicator drops available from Amazon give a clear indication with a resolution of 0.5 pH. Typically it is pH 6.0 or less. Our slate roof collected rainwater measures 6.6 pH by a council approved lab, which is just inside the permitted lower limit 6.5. We have been prescribed Juraperle granules to put in a standard clear 10" long filter housing, a few handfuls to start with, to add to as required to get up to at least neutral pH 7.2. I don't have any pH testing means. On 28/06/2024 at 19:14, sharpener said: Universal Indicator drops Did you try the electronic pen type pH meter? Quite expensive but maybe a good investment if it means preventing plumbing parts like springs inside pressure reducers being damaged. Link to comment Share on other sites More sharing options...
sharpener Posted July 1 Author Share Posted July 1 1 hour ago, Hastings said: Our slate roof collected rainwater measures 6.6 pH by a council approved lab, which is just inside the permitted lower limit 6.5. We have been prescribed Juraperle granules to put in a standard clear 10" long filter housing, a few handfuls to start with, to add to as required to get up to at least neutral pH 7.2. I don't have any pH testing means. Interesting, remind me what part of the country are you? I think if we could get a naturally occurring pH of 6.6 we would be very happy and wouldn't bother about it! Was it the testing lab who advised the Juraperle? Will a 10" filter housing be enough for your flow rate (have just reviewed my correspondence with Wrekin Water and they advised a min size 8 in dia 35 in high vessel for 10 lpm)? 1 hour ago, Hastings said: Did you try the electronic pen type pH meter? I have looked into these but I think they are more suited to regular use by the professionals. For best accuracy you need to keep the electrodes in a buffer solution when not in use and recalibrate them periodically. Universal indicator drops https://www.water-for-health.co.uk/ph-test-colour-reagent.html have a shelf life of 3 years so I ought to get some more now. And they are above all reliable and cheap! The colour chart is a bit off though, IIRC pH 7.5 is a pleasing teal colour which is not shown on the test card at all. BTW when are you going to be back on site and able to test yr pump again? Link to comment Share on other sites More sharing options...
Hastings Posted July 1 Share Posted July 1 Southern inner Hebrides. Local contractor suggested and supplied Juraperle pH correction, remotely. Surely only a rough and easy solution, given the variable flow rate expected. I am back on sit 16th July. Link to comment Share on other sites More sharing options...
SteamyTea Posted July 1 Share Posted July 1 47 minutes ago, Hastings said: Southern inner Hebrides I wonder how much the pH changes over different parts of the UK. Be a good Citizen Science project. Link to comment Share on other sites More sharing options...
Hastings Posted July 2 Share Posted July 2 (edited) We regularly get some salt from the sea sometimes but it's probably not enough to raise the pH of the rainwater in our 10,000L collection tank. Proximity to urban centers, where more SO2 is emitted, is the main factor. https://naei.beis.gov.uk/data/map-uk-das?pollutant_id=8 Acid gas and aerosol monitoring sites: https://uk-air.defra.gov.uk/interactive-map?network=aganet Edited July 2 by Hastings Link to comment Share on other sites More sharing options...
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