Hot water from our taps has suddenly started to run very slow. This morning I tried the trick of back pressuring the system to remove any airlocks by connecting the cold water feed to the washing machine to the hot water feed, and opening both taps, hot followed by cold. This seemed to work and full hot water flow was returned. This evening when I went to run a bath again same problem!! Virtually no hot water pressure. Any ideas. My only thought at the moment is that the valve isolating the hot water cylinder from the header tank is somehow faulty / blocked. Would this cause the problems I am experiencing. Any advice much appreciated. Thanks
The cold waater tank in the loft is full and ball valve is fine. Cold water from the tank loft is running fine down to the shower.
how high is the vent pipe from the cylinder terminating over the water tank?when you run the hot taps the water in the vent may drop and if its dropping below the 'tee' supplying the domestic h/w air may be drawn in....it will probably be 22mm and considerations could be made to upgrade to 28mm....check cistern is no less than 1 meter vertical between top of cyl and bottom of tank.
Run hot bath tap & check balltap maintains good pressure,if not could be slight blockage in balltap oriface.Do you live in bungalow with tank sitting on roof trusses & pipework from tank running level or bent with loads boxes,& suitcases on top causing airlocks.Have you got low pressure cold supply to bath,if so make sure tank capacity is ok if not when you fill bath you could suck air into system.Other problem could be be scale blockage on hws draw off on top fitting on cylinder, to check this disconnect the fitting from the cylinder & unscrew the fitting from the cylinder amazing sometimes how gets water gets through at all. Must be one of these faults.
The fact that you back pressured the hot water system, and then it ran for a while, sounds like debri. As a poster has said, very difficult to give advice, and we can only work from what you have said. I.E header tank full. Do you have a power shower, or a hot water pumped supply from the hot water cylinder or pipe work ?. If not, and the whole house is hot gravity fed, then I cannot see how air can gain access, regardless of the vent pipe height. (water finds its own level). It would be feasable for an air lock, or partial air lock, but I assume the system ran for a few years without a problem?.
Is the cold water storage tank covered properly? could be something has fallen in tank and blocked hot water feed outlet on tank. You need to look inside the tank and check the outlets are not obstructed. I had the same problem a while back and found a bat had fallen into cold water tank. Had to dissinfect tank. sagsy
Update. I took out the gate valve so there is definitely no constriction and had same problem occurring. The one thing that has changed is that a new ball valve was fitted in the cold water tank at Christmas. The water level in the tank after putting in the new ball valve was I think a bit lower than before. The pipe which takes the hot water to the bath, and showers is Teed off the vent pipe in the loft, less than a metre below the water level in the tank. I increased the level of water in the water tank by about an inch, and blew back to remove airlocks, and for the last 24 hours all has been well. I am wondering if this was "on a knife edge" and with a lower level in the water tank, the water level was dropping in the vent pipe just enough to allow air into the system?? If you think this is likely would you advise getting the hot water junction to the taps replumbed so it comes off much lower down and closer to the top of the hot water cylinder? Thanks for all the helpful comments on this.
kernow did you check if the cold supply to cold bath tap is tank fed or main supply.shut main cold stop tap and see if cold tap on bath still runs.
The cold water to the bath is at mains pressure. The only cold outlet from the mains tank is to the two showers.