Expert: Cortez (cort) Cate - 4/6/2005

Question
I have a hot water tank which isn't working properly no hot water. It has 2 side entry points one at the bottom which is red hot when the heating is on and one at the top which is cold then what looks like a cold feed on the other side of the tank and a vent pipe on the top. I live in a high limescale area in england and wonder if it's blocked if so can i drain the system and remove tank and clean or would you advise new tank? also can you think of any other reasoning behind this. Your thoughts would be appreciated
cheers
Mike Rodger

Answer
Hello Mike,

I will try to help you Mike, but you really need someone who is more familiar with your area.  I am in the U.S. and our conventional tanks are a little different than yours.  In as much as I do not know exactly who to send you to we will try to tackle your problem now in hopes that we can be some help immediately.

I need to know what the source of energy is, natural gas or fuel oil.  You say you are in a high lime area and it would indicate there is some internal build up by the low inlet being so hot.  You should hear some rumbling or cracking noise if the lime buildup is significant.  The cold water normally will enter at the lowest point in order for the heater to function naturally.  By that I mean, that hot water rises because as it is heated it expands and weighs less by volume than colder water.  Ever swim in a pool in summer where the water was warm on top but cold on the bottom?  Same principal is at work.

Regardless, the cold should be the low entry to the tank and the hot will be on the high part of the tank.  Perhaps the third line is a temperature and pressure relief line (T&P) because there should also be one somewhere on the top of the tank.  The T & P will normally be a ¾ inch line while the in and out lines may be larger but for residential use ¾ is sufficient for those also.  Larger in and out are usually on commercial tanks.  

If you tank has hand hold openings, (approximately 6x6 inch or larger access holes) you should examine the inside of the tank, after properly draining of course, to see what the buildup is and remove it.  If the tank does not have these access ports the only way to get the stuff (lime) out is to drain the tank and then get vinegar or some other solution that will break up the lime so you can flush it out.  All this assumes your tank does not leak because if it does that would warrant the consideration of a new tank.  The type of tank that we use in the states is not practical to repair but not knowing how yours is constructed I cannot speculate if it is worth attempting to repair but I seriously doubt that it is practical.

All that I have relayed to you is only a cursory attempt to give you some help immediately.  If you explain the complete setup perhaps I could give you better information but what I have said is (I hope) sufficient to guide you in the right direction.

Good luck, and get back to me if you want.

cort

Hi again Mike,

This web site has some diagrams of UK heating systems...Like I said before they are different than those in the U.S. so I am not real keene on them.  Use this site and if it does not answer your questions you can always come back to me.  Always give me all the information you can think of....Thanks and good luck, cort.

http://www.diydoctor.org.uk/projects/domestic_hot_water_systems.htm