Pump (isolation) valves - what's the point?

[dogfonos]

For the third time in about fifteen years, I've needed to replace an outwardly leaking central heating pump isolation ball valve (in fact, both of them this time) yet throughout that time, the circulating pump continues to chug merrily away, hence my question.

I've limited knowledge in this area so perhaps I'm misunderstanding something but aren't the valves supposed to be there to isolate the pump so that the pump could be removed and replaced without having to drain down the system? Well, from my experience (and those of several others I know), these isolation valves seem to fail far more often than the equipment they're used to isolate?!? And when the isolation valves fail, the whole system requires draining down.

I'm missing the logic here. Please enlighten me.

 

[Dan Robinson]

isolation ball valve

They are shyteerama

 

[TCCHeating]

I'm missing the logic here. Please enlighten me.

Ever heard the phrase 'you get what you pay for'?

Get some proper pump valves with gland nuts.

 

[Madrab]

Yup, you want full bore gated pump valves, and wind them closed and open again once every 6 months - open to the stop and 1/4 turn back down, keeps them from sticking

 

[Phill Peck]

http://www.toolstation.com/m/part.html?p=52920

These

 

[dogfonos]

Ah, I see. Thanks for the inputs.

Yes, I'm familiar with the phrase, 'you get what you pay for', but I don't find it to be true much of the time. Seems like it applies to plumbing though!

Until I replaced the pump isolation valves last week, I didn't even know these better products existed. This time however, I saw the ones linked above (Toolstation) and the local plumbing/heating shop showed me the gate valve type but I didn't buy them because they're slightly longer and I would have needed to alter pipework. Also, work I'm having done later this year will alter all the pipework around the boiler and pump anyway so I'll specify better isolation valves then. Hope the cheapies I fitted last six months or so.

 

[Madrab]

I believe those toolstation ones are ball valves, are they not?

 

[Phill Peck]

They are yes.
It's not the ball that's the problem on most but the spindle.
Descent ball type idolaters are fine

 

[Madrab]

I was under the impression that it was where the spindle fits through the nylon liner was where the problem lies, nylon liner expands and contracts differently than the steel during heat cycles creating the leak over time. Fair enough tho.

That being said, I'd probably still recommend proper gate type valves.

 

[Phill Peck]

Decent isolation valves don't leak