Two newbie question for the experts, but here goes...

1. Under what circumstances do you use a SINGLE non-return valve, and when
do you use a DOUBLE non-return valve ? What advantages/disadvantages does
one have over the other ?

2. Whats the difference, apart from a few pennies, between an ISOLATING
valve and a SERVICE valve ?

Q1 is for a pumped hot-water loop, and the valve is to ensure water goes the
right way round the system ie preventing the fresh cold water entering the
loop from going the shortest way round the loop and bypassing the
thermal-store heater.

Q2 is just idle curiosity.

Thanks in advance
Ron Askew

"Ron Askew" wrote in message
...
Two newbie question for the experts, but here goes...

1. Under what circumstances do you use a SINGLE non-return valve, and when
do you use a DOUBLE non-return valve ? What advantages/disadvantages does
one have over the other ?

2. Whats the difference, apart from a few pennies, between an ISOLATING
valve and a SERVICE valve ?

Q1 is for a pumped hot-water loop, and the valve is to ensure water goes
the
right way round the system ie preventing the fresh cold water entering the
loop from going the shortest way round the loop and bypassing the
thermal-store heater.

Q2 is just idle curiosity.

Thanks in advance
Ron Askew



http://www.arrowvalves.co.uk/waterre...utorials.shtml

http://www.arrowvalves.co.uk/waterre...tingvalves.doc


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1. Under what circumstances do you use a SINGLE non-return valve, and
when do you use a DOUBLE non-return valve ? What advantages/disadvantages
does one have over the other ?

Single valves are cheaper and drop less pressure. Double valves are more
reliable and required if water byelaws require a check valve, such as before
a shower, or garden tap.

2. Whats the difference, apart from a few pennies, between an ISOLATING
valve and a SERVICE valve ?

They are both the same, except a service valve has a tap connector one end,
whilst an isolating valve has compressions both ends.

Q1 is for a pumped hot-water loop, and the valve is to ensure water goes
the right way round the system ie preventing the fresh cold water entering
the loop from going the shortest way round the loop and bypassing the
thermal-store heater.

I'd always use doubles, but a single would work here, provided the schematic
of the system shows that the valve isn't being used to prevent contamination
of the supply.

Christian.

Christian McArdle wrote in message
t...
1. Under what circumstances do you use a SINGLE non-return valve, and
when do you use a DOUBLE non-return valve ? What advantages/disadvantages
does one have over the other ?

Single valves are cheaper and drop less pressure. Double valves are more
reliable and required if water byelaws require a check valve, such as
before
a shower, or garden tap.

Thanks for the reply. I'd certainly agree with the comment about
reliability - I've had problems recently with my system's hot water loop not
maintaining temperature properly when drawing off eg for a bath, and this
was worse if the pump was switched off. When the pump was on and not drawing
water, I'd then also get a rattling noise. I finally traced the problem to
the single valve not closing properly.
So I'm changing it for a double !! (or was I just unlucky?)
Thanks again
Ron