Water Isolation

[linwil]

Might be teaching my grandmother here but....

I have had a problem with gate valves that don't quite shut off recently. They allow a dribble of water through which isn't good given the recent weather. Given a normal layout which involves a gate valve adjacent to the cold water tank which isolates the water supply.

As "ball valves" and "stop valves" restrict the bore (and as we are talking about pumped systems) I had discounted their use.

However I have found some "quarter turn, full flow, ball valves". They do not restrict the flow and are as guaranteed as anything that I know of to "shut off". Cost under a fiver from plumbers merchants for a 15mm, 22 mm also available. They also look as they will fit in the same space as the gate valve so should just need 2 nuts unscrewing and a quick replacement.

Don't forget to drain the tank before you try it though!!

Regards.

[canaldrifter]

Might be teaching my grandmother here but....

I have had a problem with gate valves that don't quite shut off recently. They allow a dribble of water through which isn't good given the recent weather. Given a normal layout which involves a gate valve adjacent to the cold water tank which isolates the water supply.

As "ball valves" and "stop valves" restrict the bore (and as we are talking about pumped systems) I had discounted their use.

However I have found some "quarter turn, full flow, ball valves". They do not restrict the flow and are as guaranteed as anything that I know of to "shut off". Cost under a fiver from plumbers merchants for a 15mm, 22 mm also available. They also look as they will fit in the same space as the gate valve so should just need 2 nuts unscrewing and a quick replacement.

Don't forget to drain the tank before you try it though!!

Regards.

 

Depending on access, of course, it might be possible to turn off the gatevalve and fit the new plastic ballvalve just after it, then leave the gatevalve open permanently. Are you sure that both valves have the same thread and pipe-tail length beyond the olives?

 

In plumbing, often, nothing is as simple as it seems.

 

Tone

Edited January 8, 2011 by canaldrifter

[RobinJ]

Might be teaching my grandmother here but....

I have had a problem with gate valves that don't quite shut off recently. They allow a dribble of water through which isn't good given the recent weather. Given a normal layout which involves a gate valve adjacent to the cold water tank which isolates the water supply.

It is amazing how many systems use gate valves as stop cocks!

Stop Cock

Gate valves are designed to control the flow (at high pressure) but cannot form a complete seal especially when they are under low pressure (as from a hull tank).

As "ball valves" and "stop valves" restrict the bore (and as we are talking about pumped systems) I had discounted their use.

However I have found some "quarter turn, full flow, ball valves". They do not restrict the flow and are as guaranteed as anything that I know of to "shut off". Cost under a fiver from plumbers merchants for a 15mm, 22 mm also available. They also look as they will fit in the same space as the gate valve so should just need 2 nuts unscrewing and a quick replacement.

Don't forget to drain the tank before you try it though!!

The majority of ball valves when open maintain full flow!

[David Schweizer]

It is amazing how many systems use gate valves as stop cocks!

Stop Cock

Gate valves are designed to control the flow (at high pressure) but cannot form a complete seal especially when they are under low pressure (as from a hull tank).

 

The majority of ball valves when open maintain full flow!

Agreed. However, many of the of cheap Gate Valves supplied by people like Screwfix are not. I had to source one recently from a proper Plumbers Merchant to get a full bore gate valve.

Edited January 10, 2011 by David Schweizer

[linwil]

[The majority of ball valves when open maintain full flow!

 

I agree if on mains pressure, but..

If you take a quarter turn isolating valve as an example. A 15mm valve has a hole through the ball of about 8mm (guessing). This may or may not cause a problem on a pumped (boat) system. I was just concerned that it may "starve" the pump.

Regards

[steelaway]

Agreed. However, many of the of cheap Gate Valves supplied by people like Screwfix are not. I had to source one recently from a proper Plumbers Merchant to get a full bore gate valve.

 

 

Gate valves have been the bain of my life, I hate them.

Everytime I have to close one its a lottery - as to if its going to turn at all and I have had so many seized closed when I try to turn them back on again.

I never want to see one again - use only the ball valve type.

 

Alex

[ditchcrawler]

[The majority of ball valves when open maintain full flow!

 

 

I agree if on mains pressure, but..

If you take a quarter turn isolating valve as an example. A 15mm valve has a hole through the ball of about 8mm (guessing). This may or may not cause a problem on a pumped (boat) system. I was just concerned that it may "starve" the pump.

Regards

Use a 22mm Ball valve with suitable reducers.

[linwil]

Use a 22mm Ball valve with suitable reducers.

 

Or, as in the first post a 15mm, full bore, one