Doctor Drivel wrote:

The system works perfectly with the filling loop connected.

If the check valve fails it spurts contaminated water into the drinking
water mains.

if... if... if...

if the tap is also left open, and the mains also suffers a drop in
pressure so that it is lower than that stored in the system.

Tap off, double check valve in place, loop connected. Common occurrence,
no risk to system or water main.

Its only if some muppet starts filling it to mask some other problem
that it is an issue.

Which is common.

That's not a problem with sealed systems.

It is, if the system were not sealed and configured as they are it would
not happen.

you're repeating yourself dribble...

In the same way that someone setting the pump speed too high on a
vented system and causing pump over is not an inherent problem with
the vented system, but a problem with its installation.

A rare problem.

lol!



--
Cheers,

John.

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