Using Spring water as a PH up

Hi, I am a new grower =) . (some back ground) I did all my research etc. I found a good place to buy RO water, 2 bucks for 19.9L a pop. I am using a 20L pale for my veg reservoir.
Well, I had bought well over 1k worth of equipment .. but for the life of me, no one had ph up! Anyhow, the Ro water is about 5 And I noticed previously that spring water was really high. So... i thought, what the hell, i'll throw a 1 litre into a 19.9 litre reservoir. It brought my PH to 6.0 .. I was aiming for 5.8... but i was happy after some googling =) Anyway, I just made a second load, after i finished my calmag, nutes, etc, the PH was very low, about 4.7, I tried 1/2 litre... mixed well, was at low 5... added 250ml... i hit 5.4 i think... then got my smaller measuring cup, and tossed in 80ml ... bam!... I am at 5.8

I am a total noob, but from everything I google about water.. I think it is very safe, and healthy alternative.. or Please gently explain why this is bad. (it rose .1 on the first bucket, on about the 12/13th day of use to 6.1) so it seems stable...

feedback please

New day, looking for some input please.

I use tap water to raise my PH, So I'm sure spring water will do the same unless it has some nasty's in it any water with higher PH is fine to use.

It's fine to do this. The reason many people opt for RO or distilled water in hydroponics is due to the level of dissolved solids in their tap water. Tap water on the west coast in particular seems to have a TDS that I would consider astronomical for drinking water; it can be well over 300 ppm. My tap water is typically about 75 ppm out of the faucet, whereas RO water should be less than 15 ppm and distilled water 0 ppm.
Poland Spring bottled water measures around 20 ppm and other bottled spring waters should be similar to this. TDS as you may know is the measure of total dissolved solids in the water, typically expressed in ppm or parts per million.

Aside from disinfectants (chlorine/chloramines) and there by-products- some of which can be very harmful in their own right like trihalomethanes (ie: chloroform) or haloacetic acids (suspected carcinogens), tap water is going to contain traces of prescription drugs, heavy metals, vinyl chloride and more copious amounts of minerals which result in part from the materials used throughout the water supply network (namely the pipes). Growers are concerned with the level of certain minerals like calcium, magnesium, iron, zinc, copper and lead. The former are actually required by the plants as secondary and trace minerals, but not knowing exactly how much of what is in your water can lead to problems with nutrient absorption/lockout and also clog your lines, sprayers, etc.

If you're using bottled/distilled/RO water or if your tap water is below 150 ppm it is a good idea to add Cal-Mag or equivalent calicum/magnesium supplement to the water. Some people take their RO water and mix it with some tap water in order to achieve the desired level of dissolved solids.

The reason why some distilled/RO/bottled water varies in terms of pH has to do with the carbon dioxide dissolved in it. Water in and of itself is supposed to have a near neutral pH (7) but there will always be some carbon dioxide dissolved in water which is exposed to the open atmosphere. The carbon dioxide is slightly acidic, so it will lower the pH of the solution some.