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This pressure tank is 19 litres and available for just a few dollars

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The weight is 4kg

This one is a different brand and 100 litres

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The weight of the 100 litre tank is only 15.4kg. I believe both use a similar membrane, just obviously the 100 litre is larger. However the price of the larger one is 20x more expensive, whereas the capacity is only slightly over 5x higher.

According to the use, which is to stop a submersible well pump of 16l/minute flow from running continuously, in conjunction with a digital pressure gauge/switch (e.g. run the pump from 2 bar up to 4 bar), I believe that around 95-100 litres is an appropriate size. The end user (in Indonesia), who is not me, has a limited budget, hence considering using 5 tanks instead of 1. I can see some advantages in that the larger tank does not appear to be very high quality (higher quality tanks are available but much more expensive again), whereas the smaller tanks are cheap enough to be disposable. But maybe there is some problem with 5 tanks in series that I have overlooked which would make this a bad idea?

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  • 3
    Perhaps they might work but in parallel...
    – Solar Mike
    Aug 4 at 7:30
  • How does one connect these tanks in series? There's only a single port, yes?
    – fred_dot_u
    Aug 4 at 7:37
  • @fred_dot_u That's correct for the ones I have seen, excluding the air pressure port.
    – Solar Mike
    Aug 4 at 7:44
  • Cons would be extra space needed plus all the extra pipe connections. Almost ten times more space( unless packed so much you have trouble with repairs) and connections
    – crip659
    Aug 4 at 10:20
  • Yeah, connect them in parallel.
    – Hot Licks
    Aug 4 at 19:27
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The tanks are (should be) connected in parallel, not series. They all branch off of the cold water supply line. They can even be distributed around the building water distribution system, so long as the pipes are not absurdly small.

If a valve (1/4 turn full-port) is provided for each tank (some extra expense) they can individually be removed and replaced as needed.

Multiple smaller pressure tanks are just as functional as a single larger one, with the downside being that the group of tanks takes up more space than the single tank of larger capacity, and that it can be more complicated to diagnose problems with an individual tank in a group, particularly if individual tank valves are not provided. The upside is that a single tank failure has less extreme impacts while it's awaiting replacement, and that the space needed for each tank is smaller, which can work better for some spaces. Evidently (and not universally) in this case there also appears to be a savings of money; but there will also be additional fittings (and ideally, valves) to purchase.

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  • Shut-off valves (both inlet and outlet) for each tank is a critical detail. Good for pointing that out!
    – FreeMan
    Aug 4 at 14:24
  • Normal pressure tank has one port connected to the system - in and out are the same. "in-line" tanks exist, but are unusual.
    – Ecnerwal
    Aug 4 at 16:30
  • Ah. Fair enough. (Fortunately, don't have to deal with one at my place.)
    – FreeMan
    Aug 4 at 17:09

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