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Discuss help draining sealed ch system in the Central Heating Forum area at PlumbersForums.net

Messages
15
Hello
I have a sealed ch system that I am trying to fit a new 3 way valve (leaking) and a water pump (nocking) in one go, problem is that the two shut off valves at the pump are solid screw type and will not turn even with a large bladed screwdriver so I am stuck.
Looks like my only option will be to partially drain the system but I only want to drain it low enough to swap the pump & 3 way valve leaving the rads full, hope this makes sense
I have two drain valves that I am guessing are for emptying the system but I am not sure which one will do the job these 2 valves are located at the lowest point at the hot water cylinder one is permanently cold and the other gets hot when the boiler is heating the water.
Is my plan to lower the water above pump / 3 way valve workable, any help would be appreciated. Thanks.
 
Messages
15
Isn’t there a drain off above the boiler ?

it’s the hot one you want
The only thing I can see it where the boiler pipes go into the loft space there are two air vent valves after that the pipes come down into the airing cupboard and one goes to the hot water cylinder and the CH this is where the 2 drain valves are.
 

Marc Bowers

Gas Engineer
Messages
24
Hello
I have a sealed ch system that I am trying to fit a new 3 way valve (leaking) and a water pump (nocking) in one go, problem is that the two shut off valves at the pump are solid screw type and will not turn even with a large bladed screwdriver so I am stuck.
Looks like my only option will be to partially drain the system but I only want to drain it low enough to swap the pump & 3 way valve leaving the rads full, hope this makes sense
I have two drain valves that I am guessing are for emptying the system but I am not sure which one will do the job these 2 valves are located at the lowest point at the hot water cylinder one is permanently cold and the other gets hot when the boiler is heating the water.
Is my plan to lower the water above pump / 3 way valve workable, any help would be appreciated. Thanks.
With a sealed system you can get away with a lot of ‘live’ work, by only draining off the excess pressure and relying on the water being held in place by minimising the chance of air displacement. But, you need to know what you’re doing and be ready with a wet vac and drain down if all goes wrong. There are some fancy tools that allow valve replacement by passing through the valve and bunging the pipe but they are expensive to buy and limited in use. You could try freezing the pipes but again, expensive and best done with experience. I’d suggest that if you’re not sure which pipe to vent pressure from your best option will be to employ someone or (when you discover the right drain down point) drain down either fully or at least all the radiators above and level with the pipe work you are working on. (If in a house and the airing cupboard is upstairs, buy a screw in drain off cock, isolate the tallest radiator downstairs and replace the 1/2” rad vent with the doc and drain from there)
 
Messages
15
With a sealed system you can get away with a lot of ‘live’ work, by only draining off the excess pressure and relying on the water being held in place by minimising the chance of air displacement. But, you need to know what you’re doing and be ready with a wet vac and drain down if all goes wrong. There are some fancy tools that allow valve replacement by passing through the valve and bunging the pipe but they are expensive to buy and limited in use. You could try freezing the pipes but again, expensive and best done with experience. I’d suggest that if you’re not sure which pipe to vent pressure from your best option will be to employ someone or (when you discover the right drain down point) drain down either fully or at least all the radiators above and level with the pipe work you are working on. (If in a house and the airing cupboard is upstairs, buy a screw in drain off cock, isolate the tallest radiator downstairs and replace the 1/2” rad vent with the doc and drain from there)
Marc Thanks for the reply *** property is a bungalow *** the pump & 3 way valve are at an Hight above all the rads so only the pipe from pump into loft to worry about containing water, hoping to just leave the rads full .. my main worry is the pipe rising above the pump into the loft area which is full of water if I try to undo the pump I bet a large amount of water will come down *** the other methods you mentioned are way beyond my capabilities.
I am guessing that I will have to de-pressurize the system first and wait till the pressure gauge shows "0" as unable to be sure where to drain, If I leave the 2 vent valves in the loft closed hopefully that will stop air getting into the pipe allowing the water to drop as fast as fast the length of pipe from the pump into the loft is about 4' foot so not a long length.
Cant see any way around this problem only if those valves worked !!!!!
 

Marc Bowers

Gas Engineer
Messages
24
With a sealed system you can get away with a lot of ‘live’ work, by only draining off the excess pressure and relying on the water being held in place by minimising the chance of air displacement. But, you need to know what you’re doing and be ready with a wet vac and drain down if all goes wrong. There are some fancy tools that allow valve replacement by passing through the valve and bunging the pipe but they are expensive to buy and limited in use. You could try freezing the pipes but again, expensive and best done with experience. I’d suggest that if you’re not sure which pipe to vent pressure from your best option will be to employ someone or (when you discover the right drain down point) drain down either fully or at least all the radiators above and level with the pipe work you are working on. (If in a house and the airing cupboard is upstairs, buy a screw in drain off cock, isolate the tallest radiator downstairs and replace the 1/2” rad vent with the doc and drain from there)
Oh, and change your pump valves while you are at it.
Marc Thanks for the reply * property is a bungalow * the pump & 3 way valve are at an Hight above all the rads so only the pipe from pump into loft to worry about containing water, hoping to just leave the rads full .. my main worry is the pipe rising above the pump into the loft area which is full of water if I try to undo the pump I bet a large amount of water will come down *** the other methods you mentioned are way beyond my capabilities.
I am guessing that I will have to de-pressurize the system first and wait till the pressure gauge shows "0" as unable to be sure where to drain, If I leave the 2 vent valves in the loft closed hopefully that will stop air getting into the pipe allowing the water to drop as fast as fast the length of pipe from the pump into the loft is about 4' foot so not a long length.
Cant see any way around this problem only if those valves worked !!!!!
In actual fact the job sounds really quite easy, but then I've the benefit having done it many times before. your cheapest and most reliable option is to drain down to the radiator tops, assuming you have 1/2" vent caps in the rads. so..
1. Find your tallest radiator and turn off the TRV or Wheelhead valve and take the plastic head of the locksheild and count how many turns to turn it off fully and keep it closed.
2. Open up that radiator vent, the water should very quickly come to a stop, if it doesn't the valves are not shutting fully so find another radiator to work on.
3. When the water stops, remove the vent cap completely and insert one of these with some ptfe on the threads.
4. Open up the TRV or Wheelhead and using the drain off cock attached to a hose, drain down the system until the water stops.
5. Replace your valves, pump and zone valve.
6. Take the drain off cock out, wind the Air vent back in, open the TRV/Wheelhead and re-open the locksheild the same number of turns you closed it by.
7. Re-pressurise the system and vent through.

Obviously anything is easy with experience and I often tell my customers (Especially the DIYer's, that 95% of my work is completed using just the tools in my toolbag, unfortunately the other 5% need all the tools and equipment in my (rather large) van. and there is no telling which jobs will go belly up.

I'd obviously suggest you call in a professional but if you insist in doing it yourself, I hope the above helps.
 

Timmy D

Gas Engineer
Subscriber
Messages
196
Marc Thanks for the reply * property is a bungalow * the pump & 3 way valve are at an Hight above all the rads so only the pipe from pump into loft to worry about containing water, hoping to just leave the rads full .. my main worry is the pipe rising above the pump into the loft area which is full of water if I try to undo the pump I bet a large amount of water will come down *** the other methods you mentioned are way beyond my capabilities.
I am guessing that I will have to de-pressurize the system first and wait till the pressure gauge shows "0" as unable to be sure where to drain, If I leave the 2 vent valves in the loft closed hopefully that will stop air getting into the pipe allowing the water to drop as fast as fast the length of pipe from the pump into the loft is about 4' foot so not a long length.
Cant see any way around this problem only if those valves worked !!!!!

If it’s only that small amount of water, just get a builders rubble sack, put it under/around pump and slightly undo the pump connection. Drain the small amount of pressure/water from this point.

Should have it drain/work onable in a few mins.
 
Messages
15
Oh, and change your pump valves while you are at it.

In actual fact the job sounds really quite easy, but then I've the benefit having done it many times before. your cheapest and most reliable option is to drain down to the radiator tops, assuming you have 1/2" vent caps in the rads. so..
1. Find your tallest radiator and turn off the TRV or Wheelhead valve and take the plastic head of the locksheild and count how many turns to turn it off fully and keep it closed.
2. Open up that radiator vent, the water should very quickly come to a stop, if it doesn't the valves are not shutting fully so find another radiator to work on.
3. When the water stops, remove the vent cap completely and insert one of these with some ptfe on the threads.
4. Open up the TRV or Wheelhead and using the drain off cock attached to a hose, drain down the system until the water stops.
5. Replace your valves, pump and zone valve.
6. Take the drain off cock out, wind the Air vent back in, open the TRV/Wheelhead and re-open the locksheild the same number of turns you closed it by.
7. Re-pressurise the system and vent through.

Obviously anything is easy with experience and I often tell my customers (Especially the DIYer's, that 95% of my work is completed using just the tools in my toolbag, unfortunately the other 5% need all the tools and equipment in my (rather large) van. and there is no telling which jobs will go belly up.

I'd obviously suggest you call in a professional but if you insist in doing it yourself, I hope the above helps.
Good idea about the 1/2" drain valve it would appear that I have "myson" valves tiny little fiddley ones the thread is about 1/4" dia I have changed a one in the past and still have he old one to measure.
I am thinking that I am getting in to deep with this job clearly your experience gives you confidence as you have done this job several times before.
I am wondering just how much water is above the pump leading into the loft, is it a dangerous move to slacken the top shut of valve above the pump and try to break the seal to allow the water to drain slowly or is this just a no no *** thanks
 

Marc Bowers

Gas Engineer
Messages
24
I personally wouldn’t do it without my wet vac (but then I’m charging a customer for a professional job and it limits any mess)
Using the rubble sack idea above, I wouldn’t undo the pump connections as you would struggle to catch all the water seeping out of 360degrees of pipe. I personally would loosen (as above, only loosen, if all goes wrong you are only tightening rather than trying to replace) the four hex bolts holding the pump head onto the pump body, that way you can hold your rubble sack completely under the joint between body and head that is letting out the water, giving you a much better chance of catching it all.
no one can tell you how much water without seeing the job but it’s usually only a few litres.
 
Messages
15
I personally wouldn’t do it without my wet vac (but then I’m charging a customer for a professional job and it limits any mess)
Using the rubble sack idea above, I wouldn’t undo the pump connections as you would struggle to catch all the water seeping out of 360degrees of pipe. I personally would loosen (as above, only loosen, if all goes wrong you are only tightening rather than trying to replace) the four hex bolts holding the pump head onto the pump body, that way you can hold your rubble sack completely under the joint between body and head that is letting out the water, giving you a much better chance of catching it all.
no one can tell you how much water without seeing the job but it’s usually only a few litres.
Hi Marc
Yes understood what you are saying the Wilo pump has only two hex screws diagonally situated and I have metric allen keys so no problem, having control over the water draining is important *** as Timmy D said in an above post there should not be that much to drain *** last famous words 😂
I will make sure the bag is high and if possible above the pump height to minimise any overspill
I am yet to order the pump I will fit two new shut off valves with better quality shafts which will make life easier if I need to do further work.
Have to admit not a fan of electronics on pumps given the heat build up etc I bet any new pump won't last 20 years as the Wilo has, just wish I could find identical pump (Wilo gold 50) but not made now looking at DAB Evosta 3 still has electronics for control do you know of this pump ?
Thanks for your advice.
 

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