Testing the pH of water

[firestorm]

Tonight I was doing a test, just to see what the different pH's are of tap water, boiled tap water and distilled water. I will be hooking up my RO system as soon as I can get it put together, which apparently has no pH which distilled is supposed to neither. So I wanted to see how much tap water I will have to add to the ratio of RO/DI water. I put 1 part distilled into 10 parts tap. When I was testing the pH of all 3 the tap water had a pH of about 7.7, the boiled water had a pH of about 7.8 and the distilled water read to be about 8.0 pH, and my mix of 1:10 of distilled to tap had a reading still of around 7.7. Now my question is, isn't the pH of distilled water supposed to be very low to nothing? I used our hagen pH test kit to get the results. How am I supposed to figure out the ratio of tap to RO water, if our kit is reading the levels like this. I don't understand why the pH should be higher in these, when we have done research and everywhere we have looked it has always said that RO and distilled water have a very low to no pH, and that boiled tap water should also have a lower pH. Since the KH is very low to none at all in distilled and RO water, there should also be a low to no pH reading for them. So am I doing something wrong to get these results? How much would a pH meter cost me so I can have more accurate results? I am going to have to delay my experiment to figuring out what ratio I will need to get a softer lower pH water for my fish.

Yes I know most of the time we are told not to mess around with these things, and that our fish can live in our water where we live, but when it comes to breeding certain types of fish, it is usually required to try and lower the levels of pH and KH to get them to spawn. Our KH is around 120. I do not want to use straight RO water, for one it can be costly to do so, and I also want to avoid using chemicals to put back in the water to raise the levels to where I want them. So I have also read that by using a ratio of tap to RO will usually let me avoid doing so. Any experts or anyone with experience in using this equipment? and what do you do to get your desired levels? Thanks alot, any helpful information would be very much appreciated.

[nighthawk]

It's really going to depend on the source water. Distillation just means boiling, collecting the steam, and cooling it until liquid forms again. This will remove a large number of impurities that tend to impact the pH of water, but by no means all of them. Boiling water will, if anything, concentrate impurities, but tend to kill any little germs or other critters in the water.

All water has a pH; this number just measures the relative amount of acid and base in the water. Neutral water should have a pH of 7; from what I've read, distilled water will often be a little more acidic (i.e. lower pH), due to the CO2 it absorbs from the air in the distillation process. The hardness, (KH or DH) is a measure of the dissolved solids in the water, specifically calcium carbonate. This acts as a buffer, tending to stabilize the pH of the water. If you have water with very low hardness (DH and KH can theoretically go to zero), your water will likely be very unstable in its pH, as small amounts of impurities will cause relatively large shifts in pH. Boiling water should actually increase the hardness, as you are concentrating the impurities in the remaining water; distillation should lower the hardness.

I am no expert in the science of fish breeding yet, although I hope to be one day. I just thought that clarifying some of the terminology for you might help you make some good choices about what to use for softer, more acidic water, as well as answering some science questions for other readers. RO/DI water is gonna be expensive, but it's likely to be the best choice for softening your water supply. Manipulating pH is a little more complex, involves chemicals, and is probably going to involve a bit more trial and error.

[firestorm]

Yes I am very familiar with alot of the chemical parts of things, I am in chemistry 30 right now and know alot about pH and pOH values. There are many acids that can be lower then a pH of 1, but they have to be very concentrated, as well with bases or alkalines, some can be over 14. A pH of 7 is neutral, and we are hoping to at least get ours down to a value of about 7.2-7.0. And yes our water here is very hard with a high KH. I am just wondering if it would be impossible to do partial tap to RO with it, and hope that I don't get all kinds of pH fluctuations because of it.

I already have the RO/DI system which is my first step, I really wish I had it all hooked up because it would really help me in determining exactly what I will do. I will be doing many tests with the water before adding anything to my tank, just so I can determine the best route and combination to prevent having pH swings in my tank, definitely don't want that happening. I know that the KH will buffer the pH from going too low, and have learned the hard way from this when we first tried to lower pH without lowering KH too.

I actually didn't realize that the boiled water was more concentrated with minerals, but it does make sense. My boyfriend was the one who read that boiled water would make a lower pH and KH, but I think he got that mixed up with distilled water. So if anyone else knows a good ratio I could try in my experiment, of tap to RO, it would be beneficial, though I have read on threads that having a ratio of 10 parts tap to 1 part RO will be good. I guess that all depends on the beginning point of how high the KH and pH is to begin with. Which is why I will be running my experiments using buckets of water first I am just not sure why my pH test kit was reading the distilled at a very high pH, I can understand about the boiled water. Maybe I need to invest in a more accurate tester in the form of a meter.

[werner]

I think you are confusing pH and hardness- RO/distilled water has little or no hardness (GH or KH), but it does have a pH (around 6). Boiled water has a lower KH, but not a lower GH. Really good explanations of the differences: KH GH pH

When testing your tap water's pH, let it sit out for a day first. There is often dissolved CO2 from water treatment which will give you a false reading.

You can mix your tap water with RO water to make it softer (GH and KH), but you will probably not see a significant change in it's pH. I use a ratio of about 1 part RO:3 parts tap water. You can then start messing with the pH if you really want to, but that's much more complex issue (as nighthawk mentioned.) If your pH is around 7ish, you should be fine for most fish species.

[nyb440]

Just a couple of clarifications:

The pH of distilled, deionised, or good RO water will typically be in the 5-6 range, rather than a neutral 7, because of the uptake of CO2 from the air to form carbonic acid:

CO2 + H20 --> H2CO3.

However, because distilled water has pretty much zero buffering capacity, you can very easily get false pH readings resulting from contamination (dirty glassware, etc.) A reading of 8 is probably a result of said contamination. Odd pH measurements for distilled water can probably be ignored, as when it is mixed with water containing a buffer (i.e., tap water) the low concentration of acidic/basic species in the distilled water will make little difference.

Boiling tap water will not increase the hardness because of higher ion concentrations. Rather, as Werner alluded to, the temporary hardness is removed due to the precipitation of salts, mainly CaCO3 and MgCO3, and the concurrent evolution of CO2:

Ca2+ + 2HCO3- --> CaCO3 +CO2 + H2O

This is what causes the white deposits in your kettle, etc. What remains in the water is the permanent hardness. The measured pH may (probably not by a great amount) or may not be affected, depending on the buffering ions that were originally present/remain.

Happy pH testing!

[firestorm]

I think you are confusing pH and hardness- RO/distilled water has little or no hardness (GH or KH), but it does have a pH (around 6). Boiled water has a lower KH, but not a lower GH. Really good explanations of the differences: KH GH pH

When testing your tap water's pH, let it sit out for a day first. There is often dissolved CO2 from water treatment which will give you a false reading.

You can mix your tap water with RO water to make it softer (GH and KH), but you will probably not see a significant change in it's pH. I use a ratio of about 1 part RO:3 parts tap water. You can then start messing with the pH if you really want to, but that's much more complex issue (as nighthawk mentioned.) If your pH is around 7ish, you should be fine for most fish species.

Lol yeah I think I was mistaking the pH for KH when it comes to distilled and RO water. Wow guys I cannot believe all the helpful information you provided me with. I am in chemistry but didn't know exactly every chemical reaction the different types of water will undergo, since they tend to not focus alot on just water I will re test all the sample water today, and see what my readings are then. The distilled water is in a jug that sits out on the counter, so I don't know what's going on there. Once I get the RO unit all hooked up I will test out everything to see what I will need to do to the water to stabalize it. I don't really want to go much lower than 7 for my pH, actually neutral is more of what I am looking for. So werner, do you have to add anything back to your RO/tap combination to get it where you want it? I have read before that by using parts of each it should prevent me from having to add back alot of the minerals and chemicals to get my parameters to where I want them. Thanks again guys, this info is very helpful, and I am sure there will be others who can learn alot from this as well as me :thumbs:

[Mandy]

I don't pretend to understand any of it, but here are my results in case they help!

Tap:

pH 8.4+ (the highest my kit goes)

GH 75ppm (approx. 4 dH)

KH 300+ (again the highest my kit goes) (approx. 17dH)

RO water:

pH 6.3- (the lowest my kit goes)

GH 0

KH 0

I use 100% RO water and add the product "RO Right" because my tap water (from our well) has 1-2ppm of Ammonia naturally, so I don't want to add that to my tank.

The water in my tank:

pH 6.8

GH 75ppm (approx. 4 dH)

KH 80ppm (approx. 5 dH)

[werner]

So werner, do you have to add anything back to your RO/tap combination to get it where you want it? I have read before that by using parts of each it should prevent me from having to add back alot of the minerals and chemicals to get my parameters to where I want them.

I pretty much don't add anything back into the water- I just use the RO water to reduce the hardness of the tap water to where I want it (like I'm 'thinning' it out.) However, if you're like Mandy and have ammonia (or something else nasty in the water), you can reconstitute it entirely from RO.

The pH should probably end up just fine for you after all this, so no need to mess with it.

[firestorm]

Yeah I live right in calgary, so we are not using well water or anything. I have tested the parameters of the tap and we don't have any ammonia or nitrites in our tap water, which is probably a good thing. That is what I thought about using just partial, and it will be alot cheaper than having to use full RO water and having to add chemicals back in. All I am planning is to thin out like you said werner, which makes the most sense. I will let you know when I get my RO system hooked up and I can do all my experimental values, then I will post it here so that it may help someone else if they also have the same type of question. Thanks again guys and thanks Mandy for your values, I guess I will know if I ever have to use well water

[werner]

Here's Calgary's annual Water Quality Report. It should give you some numbers to work with.

[firestorm]

Thanks for the link werner, it should help alot.