Mains flush.......now worse than before !

[zigg]

I decided to perform a mains flush on my system, because I had taken the downstairs rads off and flushed them out, and got a load of black water out of them. (they have been cold all winter, but upstairs have been hot ish).
So I closed the two gate valves on the feed and return, and flushed the upstairs rads........great, got loads of black water out, and flushed each one til the water ran clear.....opened the gate valves and turned boiler on..............now non of the rads get hot, or even warm, bar one ( bathroom rad, which feeds and returns on the pump side of the gate valves)!!
Is it possible that a gate valve has failed in the shut pos......anyone known this to happen..??...........I can feel hot water going past the feed one, so it cant be that....
Please, any ideas guys.?...house is freezing, and wife is NOT a happy person......

 

[breezer]

i have no idea, but i can tell you i did have a gate valve stick half way, it was an "el cheapo gate valve"

it wasnt used on heating i was trying something, so it was easy to see what had happend (i am not a plumber or heating engineer)

 

[Alfredo]

More than likely a crappo gate valve. I've had them leak, fail fully open, fail fully closed, fall to bits in my hands, collapse due to dezincification..you name it..they do it.

Alfredo

 

[breezer]

you name it..they do it.

can it tap dance?

 

[Paul Barker]

The worm gear in a gate valve ensures that the shaft snaps if it encounters too much resistance but is retained so you have the sensation you are opening the valve, yet the worm gear is doing nothing.

I think my rate of failures from old gate valves is 1 in 3.

For absolutely certain change the gate valve.

At least they don't leak like ball valves.

 

[zigg]

Thanks guys, I hope that's what the problem is..................gonna drain down tomorrow and hopefully will find a nailed gatevalve.......
Is there any reason for not using a normal stopcock instead of a gate valve............or are they only used on coldwater pipes..??..excuse me if that's a stupid question.

 

[sime10]

A stop tap won't sometimes open under low pressure get a full opening ballofix

 

[Agile]

A gate valve is designed for a low pressure system for occasional use for maintenance. It has little flow resistance when open.

A stopcock is designed to resist up to 10 Bar of mains water pressure.

Have you had a balti at the Castle lately?

Tony

 

[zigg]

Hi Agile.........thnx.........you mean Castle Balti? I have to admit I've never been there..........looks good tho....bring your own alcohol,lol.

 

[ChrisR]

Use these - but only a good make such as Peglers or Conex. Plumbcenter ones are ok too.

 

[zigg]

Thanks ChrisR.........they won't leak?

 

[zigg]

Ok...........drained down and checked the gatevalves...........damn....they were both open.... ...........So removed the pump and opened it up, looked a bit nasty, but certainly not blocked with gunge... But, did notice quite a bit of endfloat in the shaft. So, decided to refit the grunfoss I had in the shed, 'cos that had no play in the shaft, and the impeller is bigger too.
Put everything back together and did a mains flush on every rad, both ways, and then included the boiler, so I was sure there wasn't a blockage anywhere.
Fired the system up with only the farthest downstairs rad on, and hot water surged down to it and filled it...so far so good.
Pump was making lots of whooshing noises, so bled it and it quietened down. Then opened up one rad at a time upstairs...and the pipes feeding downstairs went cold..........
This is driving me insane...........could it be the pump?
It is going round and on 2nd speed.......I don't know what else to do.....
Btw, does it make any diff which valve to adjust to balance the rads....or does it have to be the outlet?
Thanks guys.....I'm getting desparate...!

I havn't got any trv's .......

 

[Alfredo]

Are you sure you havn't just got an airlock somewhere in the system. This sometimes happens when you have had a system empty and refill it. Try pump on 3 temporarily, and wang(technical term) boiler stat to max..temporarily to give the whole system some welly(another technical term). It might not work, but its always fun

Alfredo

 

[zigg]

Are you sure you havn't just got an airlock somewhere in the system.

As far as I can be. I have flushed the rads from both directions to ensure this.

I turned all the upstairs rads off, and hot water began to travel to the downstairs rads, although it (only got one turned on) only got warm, and not hot. But as soon as I cracked an upstairs rad on, all flow to downstairs stopped........

 

[Alfredo]

Zigg

What you havn't made quite clear is how the system was working before you decided to flush, or whether the system has ever worked properly.

Give us some history prior to your first decision to flush. Were they working at all then?

Alfredo