retic hot water problem

[Redback]

Hi,
I have an unusual problem.

I have a Rinnai instantaneous hot water system.

This system has started making an unusual noise whenever I run my reticulation to water my lawn.

It only happens when I run the retic.

I rang rinnai and they were a bit stumped, but suggested that there may be something in the retic causing it to try and suck water back from the HWS.

When the house was built, I had a plumber cut a gate into the mains at the front of the house and the retic is fed from this.

Would there be something wrong with this gate that may be causing my problem?

cheers

[chromis]

(Moved) Thought this post may get a response in plumbing section, rather then landscaping.

[wonderplumb]

Perhaps a faulty check valve in the heater?????????

[MonkeyWrench]

Is there a non return valve built into a Ranni? The installation of an instantanious hwu should only have a full bore ball valve on the inlet to compensate for the small amount of hot water created in the fins once the tap is turned off. the last bit of heated water expands down the supply line.

Maybee the noise could be that a dueo valve(combination issolation/non return) has been used on the supply line to the hwu instead of a ball valve. After a while a dueo valve or the hwu will give way. If it is a dueo valve it will have a small round black handle, if it is a ball valve it will have a lever.

If you find it is a dueo valve turn off your hwu at the power point and contact a Plumber. Do not use.

[wonderplumb]

Rinnai's do have integral check valves, duo valve isnt really practical with them and I have seen fellas install rinnai heaters with a swing-check above the ball valve so every time the hot water is turned off it goes with a bang and a whole lot of hammer in the pipework.