shower pump draining expansion pipe

[AdrianJudd]

I know this has been mentioned before. I'm not sure it's been fully answered.

My shower pump keeps getting air in it. I'm assuming it's being pulled in from the expansion pipe. I have a simple water heater and water tank directly above. I live in a small flat and can't re-locate anything.

Is there any reason why the end of the expansion pipe can't be under the waterline in the water tank? This would mean water would be drawn into the pipe instead of air. This is how my car radiator and expansion bottle works.

This would still allow for expansion but help (not guaranteed) to prevent air being drawn back.

 

[Madrab]

The vent/expansion pipe is designed to allow air as well as hot water (in the event of thermostat failure) to vent over the CWSC. When you heat water in a non pressurised system, air bubbles are created. They need to have an avenue of escape, i.e. the vent pipe, therefore the pipe is taken from the top of the cylinder. If the pipe dipped down into the water the air would just fill the top of the cylinder until the level of the pipe was reached.
If you have a pump for a shower, the feed should be from an S Flange, that has a dip tube that sits down into the water to avoid drawing in air into the pump or an essex flange that is located a 1/4 of the way down the side of the cylinder.
You have what sound like a combination cylinder, therefore your option would be an essex flange, to avoid air being drawn into the pump. Or a combination cylinder that has an extra tapping in the side designed for pumps.

 

[RickMoore]

The difference being your car radiator is a sealed system. Your vented hot water system requires the vent to be open to atmosphere. If the pump is drawing air in then its been plumbed wrong and sorting that out really should be your objective.

 

[AdrianJudd]

The difference being your car radiator is a sealed system. Your vented hot water system requires the vent to be open to atmosphere. If the pump is drawing air in then its been plumbed wrong and sorting that out really should be your objective.

I'm not sure how to change the set up we have. Heater with flange, pipe from flange to pump, pump sitting on floor next to the heater. Cold water tank sitting above heater. There could be the possibility to the pipe from the flange being the wrong way round...how can you tell? I can take a photo when I get home.

I'm not in a position to move anything. This is frustrating. I can't remove the flange for example, to check it's condition. I'd have to remove part for the wall to get the cold water tank out.

Presently, I again have no hot water. Nothing flows with the pump turned off. Last time this happened I disconnected the pump and reconencted it. This was 1 week ago.

I am going to fit a tee to the hot water near the pump to allow me to prime the pump without flooding the flat. That will at least help me fix the issue when it happens.

 

[Hugh Jaleak]

Photo(s) would be useful. If we can see the current setup then maybe better placed to advise you.

Pump will draw from point of least resistance, hence why it is vital to make the connection at the correct point in the system. If pump is continually drawing air, it will cavitate, not only giving poor performance but will cause premature failure of the pump....

 

[AdrianJudd]

Photo(s) would be useful. If we can see the current setup then maybe better placed to advise you.

Pump will draw from point of least resistance, hence why it is vital to make the connection at the correct point in the system. If pump is continually drawing air, it will cavitate, not only giving poor performance but will cause premature failure of the pump....

Untitled

• AdrianJudd
• 24 Sep 2013
• 1

Untitled

• AdrianJudd
• 24 Sep 2013
• 1

According to the salamander pumps, the flange above is the wrong way round. However, my limited pumbing knowledge says it's the correct way round, with the pipe to pump comming out the side of the flange.

We do get a lot of air in the system. Presently, we are using the heater. Previously, we were using the boiler (broken). Both ended up with air in the pipes causing coughing and spluttering when taps turned on. Water temp is a rather hot 60C. Adjusting the thermostat makes no difference, it's still 60C. Previously, using the boiler at mucher lower temps air was present, but maybe not as bad. Our new pump is 2.0 bar, the old one was 1.6 bar (different make). The new pump has worse issues, i.e. it stops pumping water, where as the old one just spluttered lots. I'm assuming air is being sucked in from somewhere.

Due to the confined space the tank is only 1' above the top of the heater. So, there's not a huge about of pressure from the tank to the heater. The expansion pipe is also not much higher than the heater as the ceiling is low.

Last night I primed the pump again. So, all is well until next time. I checked the cold water tank whist the pump was working and there is no starvation issue.

I'd like a cheap fix. Our shower pump (goes to shower and taps in bathroom) has recently been replaced. We need a new boiler (or the old one fixing, haven't decided yet) and ideally we'd like to fix the air issue and replace the boiler with another heat only boiler. If the air issue can't be fixed cheaply, then another option would be to throw everything you see out and get a combi boiler. This would be anoying as the pump and installation was expensive. The negatove head Salamander pump works well, when it's working. Also, I dont' really like combi boilers.

 

[kbdiy]

Looking at the pic of the flange it looks like the top connection dips down after it leaves the tank. Is that the case or is it just the angle of the pic? If so this could cause air to be trapped at the top and possibly affect the side outlet as well.

 

[AdrianJudd]

Looking at the pic of the flange it looks like the top connection dips down after it leaves the tank. Is that the case or is it just the angle of the pic? If so this could cause air to be trapped at the top and possibly affect the side outlet as well.

Yes I noticed that when I took the pic. It does go down slightly to get under the wooden slat support above it. I'm going to look at it tonight to see if that can be straightened out.

You could be right. It might trap bubbles, that are later drawn back into the tank.

The hole setup was put together by the previous owner wth the knowledge he was going to move out. So, maybe it was done in a rush/on the cheap.

 

[kbdiy]

Ideally it should have a rise, however slight to allow the air out.

Every little helps

 

[AdrianJudd]

Ideally it should have a rise, however slight to allow the air out.

Every little helps

I'm going to fit a new pipe. And this time make the shelf fit the pipework, not the pipework fit around the shelf.

It's a pity I have to turn off the water using the tap behind the heater. I'm not too sure how I'll reach it to turn the inlet water off