question: i am comparing costs at them moment. if i buy a s/s tank + pump i will have to fork out min. 3.5 to 4k incl. installation. has anyone considered (or installed) a pressurised (membrane-type) tank instead (i.e. no need for pump). price for 300 l tank (volume 150l) is around 3k from grundfos and this would allow you (or me) to store the water sealed totally hygenic and with the incoming pressure from syabas (when go better pressure it will also be "stored"). so if low pressure tank will kick in with the better pressure, if no power also no problem and if no water i have the reserve water.

anyone ever thought about it? it seems actually almost cheaper and you only have to check pressure once every two years or so and increase (just like the small tank on the pump). then can last 25+ yrs.

basically a pressured tank works with the same principle as the small pressure tank on top of the water tank. there is a membrane inside that seperates air and water and incoming water compresses the air. the tank's pressure can be preset to say 1.5 bar min. as long as syabas provides more than 1.5 bar incoming pressure, the tank will fill up and store the incoming pressure. you dont need a pump in that scenario if you're OK with incoming syabas pressure. for my place, we normally have around 2.4 bar so i could fill the tank with that pressure and enjoy the water.

my problem with the standard solution is that the storage tank is open (air vent) allowing for water contamination in the tank and as a result in the piping system. i dont want that.

so a pressure tank seems like a good idea in that sense. i was just wondering if anyone has used such a setup to hear experience. no i am direct pipe only so if got water-cut i have no water. 150l would be enough to get us through a day hence the thought.

i have considered that (see the other post). unstable pressure or lower pressure than desired can be easily overcome with a one-way valve. that way i can benefit from whatever the maximum pressure is that syabas can provide during the day. in a way the tank would even out such variations.

yes i also thought about that. however the s/s tank is not sealed properly (or is there one in the market). the lids are flimsy and the airvalve is just open. this will invite germs, bakeria and god knows what. esp. since you bake the tank in the sun it would be a growing spot for unwanted things wouldnt it? or do you know of a better tank - i asked around and essentially they seem all the same.

my piping is redone just recently and is rated 15 bar max pressure. i dont think i will have any issues there at all. its more about which option will be better given hygiene consideration. 2 bar will be enough for my place so i can live with that. pricewise its roughly the same which is why i am wondering what option will be better in the long run.

ct hardware in pj told me about pressure tanks when i raised the hygiene issue. they say hospitals etc. use them but very costly. so have to settle for a smaller size. 500l usable storage is just too costly for me. cant afford that.

thanks for the feedback. i also think it might be a tight squeeze if water cut. but for increasing flow etc. should be fine because you still have incoming water to support or will the tank cut me off from syabas while the tanks pressure is above syabas pressure? then you have a very valid point and the setup is not practical.

havent thought much about the slow fill. i agree - might be an issue.

the concept is similar. however a fully conceal ss tank will not provide any water flow. also i am not sure if the normal s/s tank would be able withstand a pipe pressure, not that you can pressurise it to begin with. if you fill it there is no air pressing the water out. this why for such cases you use a pressurised tank. if i just close the air release i will have the stale water in the tank without it providing any buffer for pressure variation etc. its just standing somewhere.

i understand the problem. which is why i thought i'd be able to "lock-in" better pressure periods with a one way valve. our pressure here is actually very nice, we always have around 2.2 bar, occasionally 2.4 or 2.6 which is why i thought i can rely on them.

the hygenic issue comes from me thinking i dont need a tank at all. so we did only one hot and one cold water cycle. its all connected. so having dirty water for some outlets is sadly no option (should have done rainwater catchment for toilets or something).

my list is similar to yours, just two days reserve would be ok (need to have sufficient water exchange there). if you want to combine all points, a pressure tank seems right. i will just have to think about it some more how it works when i draw water. will call grundfos to ask.

yes there might be water mixing if the inlet & outlet are at different heights. but if you close the air valve, you basically create a mini pressure tank. assume you leave it full of air, pressure will be around what 1 bar isnt it? then incoming water presses into the tank at say 2 bar, compressing the air until equilibirum (2 bar), so i you have pressured water in the tank (with the air as contamination source but nevermind). so you essentially have a created a DIY pressure tank minus the membrane seperating air and water and minus the ability to preset a minimum pressure. if you have a one way valve at the entry this could be an option. a 500 l s/s tank could (if sealed properly - which i doubt is possible) then store approx. 250l with 2 bar pressure.

i would assume that a s/s tank can withstand those smaller pressure settings of course i dont know for sure.

thanks for all the input you guys. i knew it's a good idea to ask here