DIY Doctor UK DIY Forums

Hi All, I am new to to this site so please forgive the long winded email. as I need some advise on a plumbing issue that I have.

Ok over xmas my old emersion tank failed, it was a old copper tank and it has decided to split on me. The central heating sysetm is a indirect system with gravity water coming down from the loft. Okay I drained down the entire water system inc central heating and refitted a new immersion tank . All the pipes to and thro are 22mm copper and everything went well. I fitted a couple of gate valves for emegencies just in case I have another issue in the future for good measure.
Physically the tanks were identical however the only difference was the top connection to the central heating was 2 inches higher which I had to plumb as neccesary. Also I fitted a new tank stat due to the old one having a different clamp assembly and was not ideal for the new ready lagged tank which required a different version of attachment.

The hot water leaves the tank via a 22mm pipe and attaches it self to another 22mm pipe which feeds the rest of the house and obviously the vent pipe which leads into the attic space which is positioned about a foot off the cold water tank.

Okay up to the point before the old tank splitting I had a supajet 100 power shower and was running perfectly up to this time. Since the new instalation of the tank when ever I turn the shower on, it screams itself to death (no water i guess)so I have to pull the power cord to isolate the shower and then turn the shower to hot and let it flow for a few seconds. I then turn the mixer to off and then turn the power back on. Once this is done the shower works fine. this dosnt happen all the time thou, I guess its only happens when the water cools down in the pipes.


I didnt change any feeds to the power shower and the gate ale is fully opening as I took it off to check for incase it was blocked or faulty. I have to wait for the hot water to come thru the shower then it works otherwise it just goes mad. I disasembled the shower to check everything and everything works fine. I checked the feed from the cold water tank and that is fine as well. temperature on the tank stat is at 60 degrees and the central heating and hot water work fine. No apparant air bubbles or gurgling either.

Okay I am at a loss now as this is becoming annoying to say the least. I down loaded the manual for the shower and the only thing I can think of is that the feed powering the shower is not low enougth. The Hot water leaves the tank in a horizintal fashion and connects to the feed pipe that feeds the house via a 22mm tee. Now the feed to feed the shower is 2 inches below that main feed. I have looked in the manual and it says that it should be a least 6 inches , okay I dont mind moving it but why would this have now become an issue. I have lived in the house for 5 years and it worked fine upto the moment that the old immersion split.

Some one please put me out of my misery, this is bugging me to death as I dont want to kill the shower.

jules

juliangungho,
Most likely cause is that the pipe coming out of the top of the HW cylinder does not rise towards the vent. Air will accumulate in the pipe and when you turn on the shower it will suck the air into the pump.
Whilst you are modifying the pipework I would suggest you fit an ******* or surrey flange to separate to supply to the pump.
end
Did your new HWC have an additional side tappping about 3/4 way up the tank, if yes then connect the pump direct to this. If not I would still suggest that if you are going to modify the pipework that you fit one of the ******* or surrrey flanges. They just screw into the top boss and give you two feeds. Make sure you get the correct thread size to fit the top boss.
end

Well this is the thing , the old tanks dimensions were roughly same, I havnt altered the hot water output feed height and the shower has worked fine for all these years.

Ok well I am going to do some checking tonight but I am finking I may have to drop the shower feed down as this mite be the cause of it. If you look at the pump take off in comparison to the height of the hot water feed the shower feed is just below the overheigt of the tank and its laging. If I was to take the thickness of the tank laging into the equation I would be some what near level with the tank.


Would it be a simple as this, the shower feed is now to high because of the laggin? or do I allter the angle of the out put pipe and make it raise it self at an angle to the main pipe work instead of the original horizontal setup.

jules

There has to be a slight incline from the tank to the vent pipe connection - not much, just enough to send the bubble on a spirit level off centre by 5-10mm will be fine. Agree with desirability for using surret flange. Finally, from top of cylinder outlet to vent pipe should be at least 450mm to prevent water swirl.

Check what was screwed into the top HW outlet of the old tank you took out. There is a type of fitting called an 'S flange' this is a tube that goes down into the tank about 5" to draw the water out of the tank and not from the external pipework above the tank.

This prevents you drawing water,then air from the vent pipe.

All good plumbing places sell them, also from the likes of screwfix (usualy listed with showers and accessories). If you have replaced the HW cylinder, then you will have no problem fitting an S flange, it simply screws into the top connection.

Go to this link http://www.awin1.com/pclick.php?p=14398 ... 071&m=1228

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